Reference Manual
   CHAPTER 9. SQL Statements     

CONNECT statement [ESQL] [ISQL]

Function 

To establish a connection to a database.

Syntax 1 

CONNECT
... [ TO engine-name ]
... [ DATABASE database-name ]
... [ AS connection-name ]
... [ USER ] userid [ IDENTIFIED BY password ]

Syntax 2 

CONNECT USING connect-string

Parameters 

engine-name: { identifier | string | host-variable }

database-name: { identifier | string | host-variable }

connection-name: { identifier | string | host-variable }

userid: { identifier | string | host-variable }

password: { identifier | string | host-variable }

connect-string: { connection string | host variable }

Permissions 

None.

Side effects 

None.

See also 

GRANT statement

DISCONNECT statement

SET CONNECTION statement

Description 

The CONNECT statement establishes a connection to the database identified by database-name running on the server identified by engine-name.

Embedded SQL behavior     In Embedded SQL, if no engine-name is specified, the default local database server will be assumed (the first database server started). If no database-name is specified, the first database on the given server will be assumed.

Interactive SQL behavior     If no database or server is specified in the CONNECT statement, Interactive SQL remains connected to the current database, rather than to the default server and database. If a database name is specified without a server name, Interactive SQL will try to connect to the specified database on the current server. If a server name is specified without a database name, Interactive SQL will connect to the default database on the specified server. For example, in the following batch, the two tables are created in the same database.

CREATE TABLE t1( c1 int );
CONNECT DBA IDENTIFIED BY SQL;
CREATE TABLE t2 (c1 int );

No other database statements are allowed until a successful CONNECT statement has been executed.

(In Embedded SQL, WHENEVER, SET SQLCA and some DECLARE statements do not generate code and thus may appear before the CONNECT statement in the source file.)

The user ID and password are used for checking the permissions on SQL statements. If the password or the user ID and password are not specified, the user will be prompted to type the missing information.

In Embedded SQL, the user ID and password are used for permission checks on all dynamic SQL statements.

If you are connected to a user ID with DBA authority, you can connect to another user ID without specifying a password. (The output of DBTRAN requires this capability.) For example, if you are connected to a database as DBA, you can connect without a password with the statement:

connect other_user_id

In Embedded SQL, you can connect without a password by using a host variable for the password and setting the value of the host variable to be the null pointer.

A connection can optionally be named by specifying the AS clause. This allows multiple connections to the same database, or multiple connections to the same or different database servers, all simultaneously. Each connection has its own associated transaction. You may even get locking conflicts between your transactions if, for example, you try to modify the same record in the same database from two different connections.

Multiple connections are managed through the concept of a current connection. After a successful connect statement, the new connection becomes the current one. To switch to a different connection, use the SET CONNECTION statement. The DISCONNECT statement is used to drop connections.

For Syntax 2, a connect string is a list of parameter settings of the form keyword=value. For a description of valid settings for the connection string, see Connection parameters. The connect string must be enclosed in single quotes.

Standards and compatibility 

• SQL/92     Syntax 1 is a full SQL feature; syntax 2 is a vendor extension.

• Sybase     Open Client Embedded SQL supports a different syntax for the CONNECT statement.

Examples 

• The following are examples of CONNECT usage within Embedded SQL.

  EXEC SQL CONNECT AS :conn_name
  USER :userid IDENTIFIED BY :password;
  EXEC SQL CONNECT USER "dba" IDENTIFIED BY "sql";

• Connect to a database from Interactive SQL. Interactive SQL prompts for a user ID and a password.

  CONNECT

• Connect to the default database as DBA, from Interactive SQL. Interactive SQL promptS for a password.

  CONNECT USER "DBA"

• Connect to the sample database as the DBA, from Interactive SQL.

  CONNECT
  TO asademo
  USER DBA
  IDENTIFIED BY sql

• Connect to the sample database using a connect string, from Interactive SQL.

  CONNECT
  USING 'UID=DBA;PWD=sql;DBN=asademo'