CONNECT ──┐
 ┌─────────┘
 └─┬───────────────────────────────────────┬──┐
   └─> 
T
O ──┬─> connect-string-literal ────┤  │
            ├─> connect-parameter ─────────┤  │
            └─> connect-parameter-marker ──┘  │
 ┌────────────────────────────────────────────┘
 └─┬───────────────────────────────────────┬──┐
   └─> 
A
S ─┬────────────────────┬─────────┬┘  │
           ├─> connection-name ─┘         │   │
           ├─> connect-parameter ─────────┤   │
           └─> connect-parameter-marker ──┘   │
 ┌────────────────────────────────────────────┘
 └┬───────────────────────────────────────────────┬─> typebox (;)
  └┬─┬─> 
C
A
T
A
L
O
G ┬─> catalog-name ─────────────┬─┬┘
   │ │           ├─> catalog-parameter ────────┤ │
   │ │           └─> catalog-parameter-marker ─┤ │
   │ └─> 
S
C
H
E
M
A ─┬─> schema-name ──────────────┤ │
   │             ├─> schema-parameter ─────────┤ │
   │             └─> schema-parameter-marker ──┘ │
   └─────────────── , <──────────────────────────┘

Additional information available:

connect expressionMore Information

 connect-expression =

 ───┬──> 
D
E
F
A
U
L
T ────────────────────┬─>
    └┬─> db-specification ───────┬───┘
     └──────── , <───────────────┘

Additional information available:

More Information

 The connect expression is a character string literal that specifies
 the database environment for the connection.  You can specify the
 alias of any database declared using the DECLARE ALIAS statement in
 all modules of the application or the alias of any database attached
 using an ATTACH statement.

 The CONNECT statement associates an SQL environment with a connection
 and specifies a connection name for the association.

 An SQL environment is one or more databases that can be attached or
 detached as a unit.  When you execute a procedure, the databases that
 you specify in DECLARE ALIAS or ATTACH statements are the SQL
 environment for that procedure.  You can use the CONNECT statement to
 add another database to the current SQL environment or to substitute
 a different group of databases for the default SQL environment.

 You can issue two different CONNECT statements that attach to the
 same database, but each attach is unique.  Each CONNECT statement
 creates its own implicit transaction.

 You can use the connection name to specify a global database context
 when writing SQL modules for concurrent access to one or more
 databases.  Once you have specified a connection name in a CONNECT
 statement, you can refer to that name in subsequent SET CONNECT
 statements.  You can use a SET CONNECT statement to specify a new
 environment for a procedure to run against without having to detach
 and recompile queries.