![]() Syntax: DROP SCHEMA IF EXISTS schemaname CASCADE RESTRICT Let’s analyze the above syntax: First, specify the name of the schema from which you want to remove after the DROP SCHEMA keywords. If the specified table does not exist in the database, then it will give a warning. Courses Practice PostgreSQL also supports the deletion of a schema and its objects using the DROP SCHEMA statement. You can use this operation along with SELECT, UPDATE, INSERT, and DELETE statements. Syntax: Parameters: IF EXISTS Do not throw an error if the table does not exist. The Exists operator is said to have been met when at least one row is found in the subquery. This means that the operator is used together with a subquery. The -q runs Maven in quite mode it disables all Maven messages except error messages. In the mainClass tag, we write the fully qualified name of the main class, such as. The /with-db-transaction macro creates a transaction-aware connection from the database specification. Use IF EXISTS option to drop a table only if it exists in the database. What is Exists in PostgreSQL The PostgreSQL EXISTS operator tests whether a row (s) exists in a subquery. We can run the application with mvn -q exec:java command. ![]() ![]() If you mean running all queries together or none of them in an isolated context (so that other clients cannot change the state like the is_deleted flag while the queries run), you can wrap the separate queries into a transaction using a database transaction:ĭatabase transactions are available to ensure that multiple operations are performed atomically (i.e., all or none). UPDATE users SET is_deleted = true WHERE username = $1 What do you mean with hitting the database only once? Running one query? Then you can combine all the queries into one: IF (SELECT is_deleted FROM users WHERE username = $1) THEN
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