CONNECT TO connection_target [ AS connection_name ] [ USER connection_user_name ] CONNECT TO DEFAULT CONNECT connection_user_name DATABASE connection_target
connection_target 在几种形式之一上指定了连接的目标服务器。
TCP/IP连接
连接Unix-域套接字
TCP/IP连接
在上述形式之一中包含一个值
类型char[] 或者VARCHAR[]的宿主变量包含上述形式之一的值。
用于连接可选标识符，这样就可以指向其他命令。 这可以是一个SQL标识符或者宿主变量。
用于数据库连接的用户名。
该参数可以指定用户名和密码，使用下面形式之一 user_name/password, user_name IDENTIFIED BY password或者 user_name USING password.
用户名和密码可以是SQL标识符，字符串常量，或者宿主变量。
使用所有缺省连接参数，正如通过libpq定义的。
指定连接参数的几种变形：
EXEC SQL CONNECT TO "connectdb" AS main; EXEC SQL CONNECT TO "connectdb" AS second; EXEC SQL CONNECT TO "unix:postgresql://200.46.204.71/connectdb" AS main USER connectuser; EXEC SQL CONNECT TO "unix:postgresql://localhost/connectdb" AS main USER connectuser; EXEC SQL CONNECT TO 'connectdb' AS main; EXEC SQL CONNECT TO 'unix:postgresql://localhost/connectdb' AS main USER :user; EXEC SQL CONNECT TO :db AS :id; EXEC SQL CONNECT TO :db USER connectuser USING :pw; EXEC SQL CONNECT TO @localhost AS main USER connectdb; EXEC SQL CONNECT TO REGRESSDB1 as main; EXEC SQL CONNECT TO AS main USER connectdb; EXEC SQL CONNECT TO connectdb AS :id; EXEC SQL CONNECT TO connectdb AS main USER connectuser/connectdb; EXEC SQL CONNECT TO connectdb AS main; EXEC SQL CONNECT TO connectdb@localhost AS main; EXEC SQL CONNECT TO tcp:postgresql://localhost/ USER connectdb; EXEC SQL CONNECT TO tcp:postgresql://localhost/connectdb USER connectuser IDENTIFIED BY connectpw; EXEC SQL CONNECT TO tcp:postgresql://localhost:20/connectdb USER connectuser IDENTIFIED BY connectpw; EXEC SQL CONNECT TO unix:postgresql://localhost/ AS main USER connectdb; EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb AS main USER connectuser; EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb USER connectuser IDENTIFIED BY "connectpw"; EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb USER connectuser USING "connectpw"; EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb?connect_timeout=14 USER connectuser;
这里有一个例子程序阐述了使用宿主变量指定连接参数：
int
main(void)
{
EXEC SQL BEGIN DECLARE SECTION;
char *dbname = "testdb"; /*数据库名称*/
char *user = "testuser"; /*连接用户名*/
char *connection = "tcp:postgresql://localhost:5432/testdb";
/* 连接字符串 */
char ver[256]; /*存储版本字符串的缓冲区*/
EXEC SQL END DECLARE SECTION;
ECPGdebug(1, stderr);
EXEC SQL CONNECT TO :dbname USER :user;
EXEC SQL SELECT version() INTO :ver;
EXEC SQL DISCONNECT;
printf("version: %s\n", ver);
EXEC SQL CONNECT TO :connection USER :user;
EXEC SQL SELECT version() INTO :ver;
EXEC SQL DISCONNECT;
printf("version: %s\n", ver);
return 0;
}