Changes definitions for VAX SQL.

Additional information available:

DOMAININDEXSCHEMASTORAGE_MAPTABLE

 ALTER DOMAIN domain-name ─┬─────────────────┬─┐
                           └─> typebox (I)typebox (S) data-type ─┘ │
 ┌─────────────────────────────────────────────┘
 └─┬───────────────────────────┬──> typebox (;)
   └─┬─> sql-and-dtr-clause ─┬─┘
     └────── <───────────────┘

Additional information available:

More Informationsql and dtr clause

 Alters a domain definition.  This allows you to change the data type
 or SQL and DATATRIEVE formatting parameters for all columns defined
 using the domain, simply by changing the domain itself.  For example,
 if you want to change the data type for EMPLOYEE_ID from CHAR(5) to
 CHAR(6), you need only alter the data type for ID_DOM.  You do not
 have to alter the data type for the column EMPLOYEE_ID in the tables
 DEGREES, EMPLOYEES, JOB_HISTORY, SALARY_HISTORY, nor do you have to
 alter the column MANAGER_ID in DEPARTMENTS.

 You can alter any named domain once you have declared the schema that
 includes the domain.  If you want to alter a domain that is referred
 to in an index definition, you must first drop the index.

 If a domain definition is stored in the data dictionary, the ALTER
 DOMAIN statement alters the domain definition in the data dictionary.

 sql-and-dtr-clause =

 ─┬─> 
Q
U
E
R
Y 
H
E
A
D
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R typebox (I)typebox (S) ─┬> quoted-string ──┬─────────────────┬─>
  │                    └────── typebox (/) <────────┘                 │
  ├─> 
E
D
I
T 
S
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G typebox (I)typebox (S) quoted-string ─────────────────────────┤
  │                                                         │
  ├─> 
Q
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E
R
Y 
N
A
M
E Ftypebox (O)typebox (R) ─┬─> typebox (D)typebox (T)typebox (R) ────────┬─> typebox (I)typebox (S) quoted-string ─┤
  │                   └─> typebox (D)typebox (A)typebox (T)typebox (A)typebox (T)typebox (R)typebox (I)typebox (E)typebox (V)typebox (E) ─┘                     │
  ├─> 
D
E
F
A
U
L
T 
V
A
L
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E Ftypebox (O)typebox (R) ─┬─> typebox (D)typebox (T)typebox (R) ────────┬─> typebox (I)typebox (S) literal ────┤
  │                      └─> typebox (D)typebox (A)typebox (T)typebox (A)typebox (T)typebox (R)typebox (I)typebox (E)typebox (V)typebox (E) ─┘                  │
  ├─> 
N
O 
Q
U
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R
Y 
H
E
A
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R ──────────────────────────────────────┤
  ├─> 
N
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E
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G ───────────────────────────────────────┤
  ├─> 
N
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Y 
N
A
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E ────┬──> Ftypebox (O)typebox (R) ─┬─> typebox (D)typebox (T)typebox (R) ────────┬─────────┘
  └─> 
N
O 
D
E
F
A
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T 
V
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E ─┘         └─> typebox (D)typebox (A)typebox (T)typebox (A)typebox (T)typebox (R)typebox (I)typebox (E)typebox (V)typebox (E) ─┘

 Optional formatting clauses allow you to modify data displays or
 query characteristics for interactive SQL users and DATATRIEVE users.

 A query header specifies a string that interactive SQL or DATATRIEVE
 displays in place of the column name when it retrieves values from a
 column.  An edit string specifies a string that controls how
 interactive SQL or DATATRIEVE formats the display of values in a
 column.

 DEFAULT VALUE and QUERY NAME are active only from DATATRIEVE.

 ALTER INDEX index-name ─┐
 ┌───────────────────────┘
 └─┬────────────────────────────────┬─┬───────────────────────┬─> typebox (;)
   └┬┬─> 
N
O
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E 
S
I
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E number-bytes ──┬┬┘ └─> index-store-clause ─┘
    │├─> 
P
E
R
C
E
N
T 
F
I
L
L percentage ─┤│
    │└─> 
U
S
A
G
E ─┬─> 
U
P
D
A
T
E ─┬─────┘│
    │           └─> 
Q
U
E
R
Y ──┘      │
    └─────────────── <─────────────┘

Additional information available:

More Informationstore clause

 Changes an index.  The ALTER INDEX statement allows you to change:

  o  The characteristics of index nodes (sorted indexes only)

  o  The names of the storage area or storage areas that contain the
     index


 You cannot change:

  o  The columns that comprise an index

  o  Whether the index is UNIQUE

  o  A hashed to a sorted index

  o  A sorted index to a hashed index

 You cannot alter an index when there are other active users of the
 database.

 store-clause = STORE ─┐
 ┌─────────────────────┘
 ├─> 
I
N area-name ─────────────────────────────────────────────────┬─>
 ├─> 
R
A
N
D
O
M
L
Y 
A
C
R
O
S
S ─> ( ─┬─> area-name ─┬─> ) ───────────────────┤
 │                         └───── , <─────┘                        │
 └─> 
U
S
I
N
G ─> ( ─┬─> column-name ─┬─> ) ─┐                         │
                 └────── , <──────┘      │                         │
  ┌──────────────────────────────────────┘                         │
  └┬─> 
I
N area-name WITH LIMIT OF ─> ( ─┬─ literal ─┬─> ) ─┬─┐     │
   │                                    └──── , <───┘      │ │     │
   └────────────────────────── <───────────────────────────┘ │     │
  ┌──────────────────────────────────────────────────────────┘     │
  └─> 
O
T
H
E
R
W
I
S
E typebox (I)typebox (N) area-name ──────────────────────────────────────┘

Additional information available:

More Information

 A storage map definition for the index.  You can specify a store
 clause for indexes in a multifile schema only.  The STORE clause
 allows you to specify which storage area files will be used to store
 the index entries.

 ALTER SCHEMA ─┬─> 
P
A
T
H
N
A
M
E path-name ─┬┐
               └─> 
F
I
L
E
N
A
M
E file-spec ─┘│
 ┌──────────────────────────────────────┘
 └─> alter-root-file-params ──> alter-storage-area-params ──┐
 ┌─────────────────────────── <─────────────────────────────┘
 └─┬─┬───────────────────────────────────────────────────────────┬─┬─> typebox (;)
   │ ├─> 
A
D
D 
S
T
O
R
A
G
E 
A
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A area-name ─┬───────────> ──────────┬─┐ │ │
   │ │                               └─> 
F
I
L
E
N
A
M
E file-spec ─┘ │ │ │
   │ │   ┌─────────────────────── <────────────────────────────┘ │ │
   │ │   └─> storage-area-params ────────────────────────────────┤ │
   │ ├─> 
A
L
T
E
R 
S
T
O
R
A
G
E 
A
R
E
A area-name alter-storage-area-params ─┤ │
   │ └─> 
D
R
O
P 
S
T
O
R
A
G
E 
A
R
E
A area-name ────────────────────────────┘ │
   └───────────────────────────── <────────────────────────────────┘

Additional information available:

ADD_STORAGE_AREAALTER_STORAGE_AREADROP_STORAGE_AREA

alter root file paramsalter storage area paramsMore Informationstorage area params

 Specifies the name and file specification for a storage area you want
 to add to the schema.  You can use the ADD STORAGE AREA clause only
 on multifile databases.  The area name cannot be the same as any
 other storage area definition in the schema.

 The ADD STORAGE AREA clause creates two files, a data file with a
 file extension of .RDS and a snapshot file with a file extension of
 .SNP.  If you omit the FILENAME argument, the file specification
 takes the following defaults:

  o  Device:  the current device for the process

  o  Directory:  the current device for the process

  o  File name:  the name specified for the storage area


 The file specification is used for both the data and snapshot files
 that comprise the storage area (unless you use the SNAPSHOT FILENAME
 argument to specify a different file for the snapshot file).  Because
 the ADD STORAGE AREA clause may create two files with different file
 extensions, do not specify a file extension with the file
 specification.

 Specifies the name of an existing storage area in the schema that you
 want to alter.  You can use the ALTER STORAGE AREA clause only on
 multifile databases.

 The alter-storage-area-params are parameters that the ALTER STORAGE
 AREA clause changes.

 alter-root-file-params =

 ─┬─┬─────────────────────────> ─────────────────────────────┬─┬──>
  │ ├─> 
O
P
E
N typebox (I)typebox (S)   ──────────┬──> 
A
U
T
O
M
A
T
I
C  ─┬───────────────┤ │
  │ │                       └──> 
M
A
N
U
A
L ─────┘               │ │
  │ ├─> 
N
U
M
B
E
R typebox (O)F 
U
S
E
R
S typebox (I)typebox (S) ──> number-users ─────────────────┤ │
  │ ├─> 
N
U
M
B
E
R typebox (O)F 
B
U
F
F
E
R
S typebox (I)typebox (S) ─────> number-buffers ──────────┤ │
  │ ├─> 
N
U
M
B
E
R typebox (O)F 
V
A
X
C
L
U
S
T
E
R 
N
O
D
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S typebox (I)typebox (S) ──> number-nodes ──────┤ │
  │ ├─> 
N
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M
B
E
R typebox (O)F 
R
E
C
O
V
E
R
Y 
B
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F
F
E
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S typebox (I)typebox (S) ──> number-buffers ────┤ │
  │ ├─> 
S
N
A
P
S
H
O
T typebox (I)typebox (S) ──┬─> 
E
N
A
B
L
E
D ─┬─> 
I
M
M
E
D
I
A
T
E ─┬─┬────────┤ │
  │ │                 │            └─> 
D
E
F
E
R
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E
D ──┘ │        │ │
  │ │                 └─> 
D
I
S
A
B
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D ────────>────────┘        │ │
  │ ├─> 
D
I
C
T
I
O
N
A
R
Y typebox (I)typebox (S) ──────┬─> 
R
E
Q
U
I
R
E
D ───────┬────────────┤ │
  │ │                       └─> 
N
O
T 
R
E
Q
U
I
R
E
D ───┘            │ │
  │ ├─> 
A
D
J
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T
A
B
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E 
L
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K 
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R
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N
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L
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R
I
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Y typebox (I)typebox (S) ─┬─> 
E
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B
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E
D ──┬──────┤ │
  │ │                                   └─> 
D
I
S
A
B
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E
D ─┘      │ │
  │ ├─> 
J
O
U
R
N
A
L 
F
I
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E
N
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E file-spec ──────────────────────────┤ │
  │ ├─> 
J
O
U
R
N
A
L 
A
L
L
O
C
A
T
I
O
N typebox (I)typebox (S) ─> journal-blocks ─> typebox (B)typebox (L)typebox (O)typebox (C)typebox (K)typebox (S) ───┤ │
  │ ├─> 
J
O
U
R
N
A
L 
E
X
T
E
N
T typebox (I)typebox (S) ───> extent-blocks ──> typebox (B)typebox (L)typebox (O)typebox (C)typebox (K)typebox (S) ─────┤ │
  │ └─> 
N
O 
J
O
U
R
N
A
L ──────────────────────────────────────────┘ │
  └───────────────────────────── <─────────────────────────────┘

Additional information available:

More Information

 Parameters that control the characteristics of the database root file
 associated with the schema, or characteristics stored in the root
 file that apply to the entire database.  You can specify these
 parameters for either single-file or multifile databases.

 Note that ALTER SCHEMA does not allow you to change all root file
 parameters you can specify in CREATE SCHEMA.  You must use the EXPORT
 and IMPORT statements to change the following root file parameters:

  o  BUFFER SIZE

  o  SEGMENTED STRING STORAGE AREA

 alter-storage-area-params =

 ─┬─┬─────────────────────────> ─────────────────────────────┬─┬──>
  │ ├─> 
E
X
T
E
N
T typebox (I)typebox (S) ────────┬──> extent-pages ─> typebox (P)typebox (A)typebox (G)typebox (E)typebox (S)  ──┬────┤ │
  │ │                     └──> (extension-options) ─────┘    │ │
  │ ├─> 
S
N
A
P
S
H
O
T 
A
L
L
O
C
A
T
I
O
N typebox (I)typebox (S) ─> snp-pages ──> typebox (P)typebox (A)typebox (G)typebox (E)typebox (S) ───────┤ │
  │ └─> 
S
N
A
P
S
H
O
T 
E
X
T
E
N
T typebox (I)typebox (S) ─┬─> extent-pages ─> typebox (P)typebox (A)typebox (G)typebox (E)typebox (S) ─┬─────┘ │
  │                         └─> (extension-options) ───┘       │
  └───────────────────────────── <─────────────────────────────┘

Additional information available:

More Informationextension options

 Parameters that change the characteristics of database storage area
 files.  You can specify the same storage area parameters for either
 single-file or multifile databases, but the effect of the clauses in
 this part of an ALTER SCHEMA statement differs:

  o  For single-file databases, the storage area parameters change the
     characteristics for the single storage area in the schema

  o  For multifile databases, the storage area parameters change the
     characteristics of the RDB$SYSTEM storage area.  SQL generates an
     error if you specify RDB$SYSTEM as the area name in the ALTER
     STORAGE AREA clause, so specifying the parameters in this part of
     the ALTER SCHEMA statement is the only way to change the
     parameters of the RDB$SYSTEM storage area using ALTER SCHEMA.


 Note that ALTER SCHEMA does not allow you to change all storage area
 parameters you can specify in CREATE SCHEMA.  You must use the EXPORT
 and IMPORT statements to change the following root file parameters:

  o  ALLOCATION

  o  PAGE SIZE

  o  PAGE FORMAT

  o  THRESHOLDS

  o  INTERVAL

  o  SNAPSHOT FILENAME

 extension-options =

 ──> ( 
M
I
N
I
M
U
M typebox (O)F min-pages PAGES, ─┐
 ┌──────────────────────────────────┘
 └─> 
M
A
X
I
M
U
M typebox (O)F max-pages PAGES, ┐
 ┌───────────────────────────────┘
 └─> 
P
E
R
C
E
N
T 
G
R
O
W
T
H typebox (I)typebox (S) growth ) ──>

 Changes the number of pages of each snapshot or storage area file
 extent.

 Deletes the specified storage area definition and the associated data
 and snapshot files.  You can use the DROP STORAGE AREA clause only on
 multifile databases.

 To protect against accidental data deletion, the ALTER SCHEMA
 statement fails if you specify a DROP STORAGE AREA clause that names
 a storage area referred to in any storage map.  You must first use
 the ALTER STORAGE MAP statement to move the data to another storage
 area.

 Alters a schema in any of the following ways:

  o  For both single-file and multifile databases, changes
     characteristics of the database root file associated with a
     schema.  ALTER SCHEMA allows you to override certain
     characteristics specified in the root file parameters of a CREATE
     SCHEMA statement, such as whether a snapshot file is disabled.
     In addition, ALTER SCHEMA lets you control other characteristics
     you cannot specify in CREATE SCHEMA root file parameters, such as
     whether after-image journaling is enabled.

  o  For both single-file and multifile databases, changes storage
     area parameters.

  o  For multifile databases only, adds, alters, or drops storage
     areas.

 storage-area-params =

 ─┬─┬──────────────────────────>─────────────────────────────┬─┬──>
  │ ├─> 
A
L
L
O
C
A
T
I
O
N typebox (I)typebox (S) ───> number-pages ────> typebox (P)typebox (A)typebox (G)typebox (E)typebox (S) ─────────┤ │
  │ ├─> 
P
A
G
E 
S
I
Z
E typebox (I)typebox (S) ────> page-blocks ─────> typebox (B)typebox (L)typebox (O)typebox (C)typebox (K)typebox (S) ────────┤ │
  │ ├─> 
P
A
G
E 
F
O
R
M
A
T typebox (I)typebox (S) ──┬────> 
U
N
I
F
O
R
M ────┬────────────────┤ │
  │ │                    └────> 
M
I
X
E
D ──────┘                │ │
  │ ├─> 
T
H
R
E
S
H
O
L
D
S typebox (A)typebox (R)typebox (E) ( val1 ─┬──────────────────────┬─> ) ─┤ │
  │ │                          └─> ,val2 ─┬──────────┬┘      │ │
  │ │                                     └─> ,val3 ─┘       │ │
  │ ├─> 
I
N
T
E
R
V
A
L typebox (I)typebox (S) ───────> number-data-pages ──────────────┤ │
  │ ├─> 
E
X
T
E
N
T typebox (I)typebox (S) ────┬──> extent-pages ────> typebox (P)typebox (A)typebox (G)typebox (E)typebox (S) ────┬────┤ │
  │ │                 └──> (extension-options)──────────┘    │ │
  │ ├─> 
S
N
A
P
S
H
O
T 
F
I
L
E
N
A
M
E ───> file-spec ────────────────────┤ │
  │ ├─> 
S
N
A
P
S
H
O
T 
A
L
L
O
C
A
T
I
O
N typebox (I)typebox (S) ──> snp-pages ──> typebox (P)typebox (A)typebox (G)typebox (E)typebox (S) ──────┤ │
  │ └─> 
S
N
A
P
S
H
O
T 
E
X
T
E
N
T typebox (I)typebox (S) ─┬─> extent-pages ──> typebox (P)typebox (A)typebox (G)typebox (E)typebox (S) ─┬────┘ │
  │                         └─> (extension-options) ────┘      │
  └─────────────<─────────────────────────────────────<────────┘

 Parameters that control the characteristics of the storage area.

 ALTER STORAGE MAP map-name ─┐
 ┌───────────────────────────┘
 └─┬─┬─> store-clause ─────────────────────┬─┬─> typebox (;)
   │ ├─> 
P
L
A
C
E
M
E
N
T 
V
I
A 
I
N
D
E
X index-name ───┤ │
   │ └─┬─> 
E
N
A
B
L
E ──┬─> 
C
O
M
P
R
E
S
S
I
O
N ───────┘ │
   │   └─> 
D
I
S
A
B
L
E ─┘                        │
   └─────────────────── <────────────────────┘

Additional information available:

More Informationstore clause

 Changes an existing storage map.  A storage map controls which rows
 of a table are stored in which storage areas in a multifile database.

 In addition to changing storage maps, ALTER STORAGE MAP has options
 that change:

  o  Which index the database system uses when inserting rows in the
     table

  o  Whether the rows of the table will be stored in a compressed
     format

 store-clause = STORE ─┐
 ┌─────────────────────┘
 ├─> 
I
N area-name ─────────────────────────────────────────────────┬─>
 ├─> 
R
A
N
D
O
M
L
Y 
A
C
R
O
S
S ─> ( ─┬─> area-name ─┬─> ) ───────────────────┤
 │                         └───── , <─────┘                        │
 └─> 
U
S
I
N
G ─> ( ─┬─> column-name ─┬─> ) ─┐                         │
                 └────── , <──────┘      │                         │
  ┌──────────────────────────────────────┘                         │
  └┬─> 
I
N area-name WITH LIMIT OF ─> ( ─┬─ literal ─┬─> ) ─┬─┐     │
   │                                    └──── , <───┘      │ │     │
   └────────────────────────── <───────────────────────────┘ │     │
  ┌──────────────────────────────────────────────────────────┘     │
  └─> 
O
T
H
E
R
W
I
S
E typebox (I)typebox (N) area-name ──────────────────────────────────────┘

Additional information available:

More Information

 A new storage map definition that replaces the existing storage map.
 The store clause allows you to specify which storage area files will
 be used to store rows from the table:

  o  All rows of a table can be associated with a single storage area.

  o  Rows of a table can be randomly distributed among several storage
     areas.

  o  Rows of a table can be systematically distributed, or
     partitioned, among several storage areas by specifying upper
     limits on the values for a column in a particular storage area.

 ALTER TABLE ──> table-name ──┐
 ┌────────────────────────────┘
 └─┬─┬─> 
A
D
D ─┬─> typebox (C)typebox (O)typebox (L)typebox (U)typebox (M)typebox (N) add-col-definition ─────────┬──> typebox (;)
   │ │        └─> 
C
O
N
S
T
R
A
I
N
T check-table-constraint ─┤
   │ ├─> 
A
L
T
E
R alter-col-definition ─────────────────┤
   │ └─> 
D
R
O
P ─┬─> typebox (C)typebox (O)typebox (L)typebox (U)typebox (M)typebox (N) column-name ───────────────┤
   │           └─> 
C
O
N
S
T
R
A
I
N
T constraint-name ───────┤
   └──────────────────── <───────────────────────────┘

 check-table-constraint =
 ──> 
C
H
E
C
K (predicate) ─┬───────────────────────────────┬─>
                        └─> 
D
I
A
G
N
O
S
T
I
C constraint-name ─┘

 The ALTER TABLE statement adds, modifies, or deletes columns in a
 base table.

Additional information available:

ADD_COLUMNADD_CONSTRAINTALTER_COLUMNDROP_COLUMN
DROP_CONSTRAINT

 The ADD COLUMN clause creates an additional column in the table.  SQL
 adds the column to the right of the existing columns in the table.

 add-col-definition =
 ──> column-name ─┬─> data-type ───┬┬┬──────────>──────────────┬┬─>
                  └─> domain-name ─┘│├─> check-col-constraint ─┤│
                                    │└─> sql-and-dtr-clause ───┘│
                                    └───────────<───────────────┘
 check-col-constraint =
 ─> 
C
H
E
C
K (predicate) ──┬───────────────────────────────┬─>
                        └─> 
D
I
A
G
N
O
S
T
I
C constraint-name ─┘

 Specify a name for the column, a data type or domain, and,
 optionally, a check column constraint and formatting and DATATRIEVE
 clauses.

Additional information available:

data typescheck col constraintsql and dtr clause

 data-type =

 ──┬─> 
C
H
A
R ─┬────────┬───────────────────────────┬──>
   │         └─> (n) ─┘                           │
   ├─> 
V
A
R
C
H
A
R (n) ───────────────────────────────┤
   ├─> 
L
O
N
G 
V
A
R
C
H
A
R ──────────────────────────────┤
   ├─> 
S
M
A
L
L
I
N
T ──┬─┬────────┬────────────────────┤
   ├─> 
I
N
T
E
G
E
R ───┤ └─> (n) ─┘                    │
   ├─> 
Q
U
A
D
W
O
R
D ──┘                               │
   ├─> 
D
E
C
I
M
A
L ─┬─┬─────────────────────────────┬─┤
   ├─> 
N
U
M
E
R
I
C ─┘ └─> ( ──> n ─┬────────┬─> ) ──┘ │
   │                           └─> , n ─┘         │
   ├─> 
F
L
O
A
T ─┬────────┬──────────────────────────┤
   │          └─> (n) ─┘                          │
   ├─> 
R
E
A
L ──────────────────────────────────────┤
   ├─> 
D
O
U
B
L
E 
P
R
E
C
I
S
I
O
N ──────────────────────────┤
   └─> 
D
A
T
E ──────────────────────────────────────┘

 The CHECK (predicate) clause creates a CHECK column constraint
 definition associated with the column.  A CHECK constraint specifies
 a predicate that column values inserted into the table must satisfy.
 Predicates in CHECK column constraints can refer only to the column
 with which they are associated.

 The DIAGNOSTIC clause specifies a name for the constraint.  The name
 is used in error messages and ALTER TABLE DROP CONSTRAINT, SHOW
 TABLE, DECLARE TRANSACTION and SET TRANSACTION statements.  The
 DIAGNOSTIC clause is optional.  If you omit the constraint name, SQL
 creates a name.  However, DIGITAL recommends that you always name
 column and table constraints.  The constraint names generated by SQL
 may be obscure and, in programs, may change between compilation and
 running.

 sql-and-dtr-clause =

 ─┬─> 
Q
U
E
R
Y 
H
E
A
D
E
R typebox (I)typebox (S) ─┬> quoted-string ──┬─────────────────┬─>
  │                    └────── typebox (/) <────────┘                 │
  ├─> 
E
D
I
T 
S
T
R
I
N
G typebox (I)typebox (S) quoted-string ─────────────────────────┤
  │                                                         │
  ├─> 
Q
U
E
R
Y 
N
A
M
E Ftypebox (O)typebox (R) ─┬─> typebox (D)typebox (T)typebox (R) ────────┬─> typebox (I)typebox (S) quoted-string ─┤
  │                   └─> typebox (D)typebox (A)typebox (T)typebox (A)typebox (T)typebox (R)typebox (I)typebox (E)typebox (V)typebox (E) ─┘                     │
  ├─> 
D
E
F
A
U
L
T 
V
A
L
U
E Ftypebox (O)typebox (R) ─┬─> typebox (D)typebox (T)typebox (R) ────────┬─> typebox (I)typebox (S) literal ────┤
  │                      └─> typebox (D)typebox (A)typebox (T)typebox (A)typebox (T)typebox (R)typebox (I)typebox (E)typebox (V)typebox (E) ─┘                  │
  ├─> 
N
O 
Q
U
E
R
Y 
H
E
A
D
E
R ──────────────────────────────────────┤
  ├─> 
N
O 
E
D
I
T 
S
T
R
I
N
G ───────────────────────────────────────┤
  ├─> 
N
O 
Q
U
E
R
Y 
N
A
M
E ────┬──> Ftypebox (O)typebox (R) ─┬─> typebox (D)typebox (T)typebox (R) ────────┬─────────┘
  └─> 
N
O 
D
E
F
A
U
L
T 
V
A
L
U
E ─┘         └─> typebox (D)typebox (A)typebox (T)typebox (A)typebox (T)typebox (R)typebox (I)typebox (E)typebox (V)typebox (E) ─┘

 Optional formatting clauses allow you to modify data displays or
 query characteristics for interactive SQL users and DATATRIEVE users.

 A query header specifies a string that interactive SQL or DATATRIEVE
 displays in place of the column name when it retrieves values from a
 column.  An edit string specifies a string that controls how
 interactive SQL or DATATRIEVE formats the display of values in a
 column.

 DEFAULT VALUE and QUERY NAME are active only from DATATRIEVE.

 The ADD CONSTRAINT clause adds a CHECK table constraint definition.
 A CHECK constraint specifies a predicate that column values inserted
 into the table must satisfy.

 Predicates in CHECK table constraints can refer to any column in the
 table.  Column select expressions within the predicate can refer to
 other tables in the schema.

 The DIAGNOSTIC clause specifies a name for the constraint.  The name
 is used in error messages and ALTER TABLE DROP CONSTRAINT, SHOW
 TABLE, DECLARE TRANSACTION and SET TRANSACTION statements.  The
 DIAGNOSTIC clause is optional.  If you omit the constraint name, SQL
 creates a name.  However, DIGITAL recommends that you always name
 column and table constraints.  The constraint names generated by SQL
 may be obscure and, in programs, may change between compilation and
 running.

 The ALTER COLUMN clause modifies the column specified by the column
 name:

 alter-col-definition =
 ──> column-name ─┬────────────────┬┬┬──────────> ─────────────┬┬─>
                  ├─> data-type ───┤│└─> sql-and-dtr-clause ───┘│
                  └─> domain-name ─┘└────────── <───────────────┘

Additional information available:

More Informationdata typessql and dtr clause

 You can modify some elements of a column definition but not others:

  o  You cannot change the column name.

  o  You can change an explicitly specified data type to another, but
     use care (see notes in this argument description).

  o  You can change the domain referred to by a column, provided the
     domain exists in the schema

  o  You can substitute an explicit data type for a column that
     previously referred to a domain name

  o  You cannot change an existing column constraint or add column
     constraints to an existing column.

  o  You can change formatting and DATATRIEVE clauses.

 data-type =

 ──┬─> 
C
H
A
R ─┬────────┬───────────────────────────┬──>
   │         └─> (n) ─┘                           │
   ├─> 
V
A
R
C
H
A
R (n) ───────────────────────────────┤
   ├─> 
L
O
N
G 
V
A
R
C
H
A
R ──────────────────────────────┤
   ├─> 
S
M
A
L
L
I
N
T ──┬─┬────────┬────────────────────┤
   ├─> 
I
N
T
E
G
E
R ───┤ └─> (n) ─┘                    │
   ├─> 
Q
U
A
D
W
O
R
D ──┘                               │
   ├─> 
D
E
C
I
M
A
L ─┬─┬─────────────────────────────┬─┤
   ├─> 
N
U
M
E
R
I
C ─┘ └─> ( ──> n ─┬────────┬─> ) ──┘ │
   │                           └─> , n ─┘         │
   ├─> 
F
L
O
A
T ─┬────────┬──────────────────────────┤
   │          └─> (n) ─┘                          │
   ├─> 
R
E
A
L ──────────────────────────────────────┤
   ├─> 
D
O
U
B
L
E 
P
R
E
C
I
S
I
O
N ──────────────────────────┤
   └─> 
D
A
T
E ──────────────────────────────────────┘

 sql-and-dtr-clause =

 ─┬─> 
Q
U
E
R
Y 
H
E
A
D
E
R typebox (I)typebox (S) ─┬> quoted-string ──┬─────────────────┬─>
  │                    └────── typebox (/) <────────┘                 │
  ├─> 
E
D
I
T 
S
T
R
I
N
G typebox (I)typebox (S) quoted-string ─────────────────────────┤
  │                                                         │
  ├─> 
Q
U
E
R
Y 
N
A
M
E Ftypebox (O)typebox (R) ─┬─> typebox (D)typebox (T)typebox (R) ────────┬─> typebox (I)typebox (S) quoted-string ─┤
  │                   └─> typebox (D)typebox (A)typebox (T)typebox (A)typebox (T)typebox (R)typebox (I)typebox (E)typebox (V)typebox (E) ─┘                     │
  ├─> 
D
E
F
A
U
L
T 
V
A
L
U
E Ftypebox (O)typebox (R) ─┬─> typebox (D)typebox (T)typebox (R) ────────┬─> typebox (I)typebox (S) literal ────┤
  │                      └─> typebox (D)typebox (A)typebox (T)typebox (A)typebox (T)typebox (R)typebox (I)typebox (E)typebox (V)typebox (E) ─┘                  │
  ├─> 
N
O 
Q
U
E
R
Y 
H
E
A
D
E
R ──────────────────────────────────────┤
  ├─> 
N
O 
E
D
I
T 
S
T
R
I
N
G ───────────────────────────────────────┤
  ├─> 
N
O 
Q
U
E
R
Y 
N
A
M
E ────┬──> Ftypebox (O)typebox (R) ─┬─> typebox (D)typebox (T)typebox (R) ────────┬─────────┘
  └─> 
N
O 
D
E
F
A
U
L
T 
V
A
L
U
E ─┘         └─> typebox (D)typebox (A)typebox (T)typebox (A)typebox (T)typebox (R)typebox (I)typebox (E)typebox (V)typebox (E) ─┘

 Optional formatting clauses allow you to modify data displays or
 query characteristics for interactive SQL users and DATATRIEVE users.

 A query header specifies a string that interactive SQL or DATATRIEVE
 displays in place of the column name when it retrieves values from a
 column.  An edit string specifies a string that controls how
 interactive SQL or DATATRIEVE formats the display of values in a
 column.

 DEFAULT VALUE and QUERY NAME are active only from DATATRIEVE.

 The DROP COLUMN statement deletes the specified column.

 The DROP CONSTRAINT statement deletes the specified column constraint
 or table constraint from the table definition.