在PostgreSQL中,我们可以在创建用户时使用“CREATE USER IF NOT EXISTS”语句。例如,以下是一个创建用户的示例代码: CREATE USER'new_user'WITH PASSWORD'password'; 这段代码的意思是:如果当前会话中不存在名为“new_user”的用户,那么就会执行上面的语句,创建一个名为“new_user”的用户,并设置密码为“password”...
I am new to postgreSQL and I am trying to create a schema file which will contain all the scripts required to create the database and required tables. The way I used to do this for SQl server was to check if the database exists and then run the necessary scripts. The following script...
在PostgreSQL数据库中,CREATE USER命令用于创建新的数据库用户。然而,在某些情况下,我们可能希望仅在用户不存在时创建用户。本文将介绍如何使用CREATE USER IF NOT EXISTS语句实现这一目的。 基本语法 CREATE USER IF NOT EXISTS语句的语法如下: CREATEUSERIFNOTEXISTSusernameWITHPASSWORD'password'; 其中: username:要创...
You could simply DROP AGGREGATE IF EXISTS array_agg_mult(anyarray); prior to your CREATE AGGREGATE Note that this may throw an error if you change the parameters/signature, so you'd need to adjust for that if you do. Manual Reference: https://www.postgresql.org/docs/current/static/sql-d...
Understanding PostgreSQL “CREATE TABLE IF NOT EXISTS” Statement If a database already has a table with the same name, then a "relation already exists" error will appear in Postgres. To avoid such a situation, PostgreSQL provides anIF NOT EXISTSclause that can be used with theCREATE TABLEcom...
Create if not exists方法是一种用于数据库操作的语句,用于在数据库中创建表或索引之前先检查它们是否已经存在。如果不存在,则创建;如果已经存在,则不执行任何操作。 这种方法的优势在于可以避免重复创建表或索引,减少了不必要的开销和错误。它可以确保数据库结构的一致性,并提高数据库的性能和可靠性。
CREATE OR REPLACE FUNCTION add_user_if_not_exists(username NAME, pw TEXT) RETURNS integer AS $$ BEGIN IF NOT EXISTS ( SELECT FROM pg_roles WHERE rolname = username) THEN EXECUTE FORMAT('CREATE ROLE "%I" PASSWORD %L', username, pw); END IF; RETURN NULL; END; $$ language plpgsql; ...
CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] name ] ON [ ONLY ] table_name [ USING method ] ( { column_name | ( expression ) } [ COLLATE collation ] [ opclass [ ( opclass_parameter = value [, ... ] ) ] ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ...
CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] table_name OF type_name [ ( { column_name [ WITH OPTIONS ] [ column_constraint [ ... ] ] | table_constraint } [, ... ] ) ]
/* If not NULL, Executor is active; call ExecutorEnd eventually: */ QueryDesc *queryDesc; /* info needed for executor invocation */ /* If portal returns tuples, this is their tupdesc: */ TupleDesc tupDesc; /* descriptor for result tuples */ ...