![]() ![]() The IF NOT EXISTS functionality was added in PostgreSQL 9.1 ( release notes). In other words, just because a table of that name already exists, it doesn’t mean it has the correct definition. It simply checks that there’s no existing table with the same name that we’re trying to give to the table that we’re creating. Note that the IF NOT EXISTS clause does not check the table structure/definition. This time we get an error: ERROR: relation "t1" already exists Here’s what happens when we don’t use the IF NOT EXISTS clause when trying to create a table that already exists: CREATE TABLE t1 ( We don’t get an error, we get a notice: NOTICE: relation "t1" already exists, skippingĪs expected, the notice tells us that the table already exists. If the user already exists, skips all password related checks. If we attempt to create that table again: CREATE TABLE IF NOT EXISTS t1 ( If true, does not inspect the database for password changes. In this case I get True, which means that the table does exist and that I have access to it.ĭepending on your configuration, you may get t/ f instead of True/ False. you can add IF EXISTS or IF NOT EXISTS: ALTER table person add column IF. We can query the pg_tables view to check to see if the table now exists: SELECT EXISTS ( SQL statement in a database console and create this table: If necessary. In that case, the table will only be created if there isn’t already one called t1. Here, t1 is the table name, and everything between the parentheses is the table definition (i.e. An error occurs if the database exists and you did not specify IF NOT EXISTS. ![]() Here’s an example to demonstrate: CREATE TABLE IF NOT EXISTS t1 ( CREATE SCHEMA is a synonym for CREATE DATABASE. of the database ( hsqldb, h2, oracle, mysql, postgresql, and so on). If a table already exists with that name, a “notice” will be issued instead of an error. It defaults to create-drop if no schema manager has been detected or none in. Craig Ringer at 1:22 It is great folly to think that SQL code written for one RDBMs (MySQL, Pg, Oracle, SS, etc) can be used by another. In a plpgsql context, you should use GET DIAGNOSTICS combined with ROWCOUNT. It can be used in contexts like CREATE TABLE IF NOT EXISTS foo. I think you're better off looking at schema migration tools like Liquibase. IF NOT EXISTS is not valid in that context within (what appears like) plpgsql. The table will only be created if no other table exists with the same name. It just hopes the table with the same name happens to have the definition you want. ![]() In PostgreSQL, you can use the IF NOT EXISTS clause of the CREATE TABLE statement to check whether or not a table of the same name already exists in the database before creating it. ![]()
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