I would like to perform a DROP VIEW IF EXISTS... command on an Oracle DB as it can be done on a MySQL database. Use this statement to remove a materialized view from the database. Summary: in this tutorial, you will learn how to use the Oracle DROP VIEW statement to drop a view from the database. In the dialect for procedural SQL in MSSQL and Sybase, there's a useful little idiom for checking whether rows exist on a table, and it looks like this... if exists (select 'x' from foo where bar) /* found, do something */ else /* not found, do something else */ As you can see, the status of the salesman_contacts view is INVALID. If you skip the schema name, Oracle assumes that the view is in your own schema. Oracle Database does not drop views, materialized views, and synonyms that are dependent on the view but marks them INVALID. Copyright © 2020 Oracle Tutorial. The world's most popular open source database MySQL.com; Downloads; Documentation; Developer Zone; Developer Zone Downloads MySQL.com All indexes and keys for the materialized view are dropped as well. Syntax DROP MATERIALIZED VIEW [ IF EXISTS] [ owner. The Oracle EXISTS operator is a Boolean operator that returns either true or false. Oracle Database does not drop views, materialized views, and synonyms that refer to the view but marks them INVALID. Oracle Database does not drop views, materialized views, and synonyms that are dependent on the view but marks them INVALID. Therefore, you cannot subsequently either purge or undrop the materialized view. If you omit CASCADE, then Oracle Database does not drop the primary key or unique constraint if any foreign key references it. This statement dropped not only the brands table but also the foreign key constraint fk_brand from the cars table.. try this (i'm not up on oracle syntax, so if my variables are ify, please forgive me): declare @count int select @count=count(*) from all_tables where table_name='Table_name'; if @count>0 BEGIN DROP TABLE … If the view belongs to a schema, you must also explicitly specify the name of the schema to which the view belongs. an alternative: A view is defined as a virtual table whose contents are defined by a query. Oracle does not provide IF EXISTS clause in the DROP TABLE statement, but you can use a PL/SQL block to implement this functionality and prevent from errors then the table does not exist. If you omit this clause, and such constraints exist, then the DROP statement fails. Drop Not null or check constraints SQL> desc emp. The following list contains various ways to put a view to good use. SQL> desc emp drop unique constraint oracle View Drop View SQL> SQL> BEGIN 2 FOR i IN (SELECT null FROM user_views WHERE view_name = 'BOOKS_emp' ) LOOP 3 EXECUTE IMMEDIATE 'DROP VIEW books_emp' ; 4 END LOOP; 5 END; 6 / PL/SQL procedure successfully completed. It works fine if the object exists in the database. Existing user tables and views can be listed by querying the data dictionary. Security can be placed on view to restrict users. To learn if the view has any subviews, query the SUPERVIEW_NAME column of the USER_, ALL_, or DBA_VIEWS data dictionary views. Oracle Database does not drop views, materialized views, and synonyms that refer to the view but marks them INVALID. DROP VIEW kinds; Compatibility This command conforms to the SQL standard, except that the standard only allows one view to be dropped per command, and apart from the IF EXISTS option, which is a PostgreSQL extension. Now Dropping the Not Null constraints. If you do not specify a schema, then Oracle Database looks for the analytic view in your own schema. To remove a view from a database, you use the DROP VIEW statement as follows: DROP VIEW [ IF EXISTS] schema_name.view_name; In this syntax, you specify the name of the view that you want to drop after the DROP VIEW keywords. If I try to create it, it says Name already exists. Oracle EXISTS for beginners and professionals with examples on insert, select, update, delete, table, view, join, key, functions, procedures, indexes, cursor etc. First, you specify the name of schema that contains the view. Therefore, the following syntax is not valid in Oracle: DROP TRIGGER IF EXISTS trigger_name; If Oracle included a “DROP object IF EXISTS” syntax like mySQL, and maybe even a “CREATE object IF MISSING” syntax, it would be a real bonus. Prior to SQL Server 2016 using DROP IF EXISTS option included writing lengthy IF statement wrappers code. @delimiter ++; declare v_exist number(1); begin SELECT COUNT(*) INTO v_exist FROM user_tables WHERE table_name = 'FOO'; if v_exist = 1 then execute immediate 'drop table FOO'; end if; execute immediate 'CREATE TABLE FOO (bar number(1))'; end; SELECT bar FROM FOO; Select all Open in new window. Equivalent for EXISTS() in an IF statement? Oracle drop table if exists Oracle Database Tips by Donald Burleson January 1, 2015 Question: I need to write code to test if an Oracle table exists ands then drop and re-create the table: ORA-00942 is one of the many errors which Oracle developer ,Oracle DBA often gets.. If any subviews have been defined on view, then the database invalidates the subviews as well. You can drop them or redefine views and synonyms, or you can define other views in such a way that the invalid views and synonyms become valid again. Specify the name of the view to be dropped. In some cases, an object not being present when you try to drop it signifies something is very wrong, but for many scripts it’s no big deal. In MySQL 8.0, DROP VIEW fails if any views named in the argument list do not exist. You can check the status of a view by querying data from the user_objects view. The EXISTS operator is often used with a subquery to test for the existence of rows: SELECT * FROM table_name WHERE EXISTS (subquery); The EXISTS operator returns true if the subquery returns any rows, otherwise, it returns false. If you don’t do so, then the DROP VIEW statement will fail in case such constraints exist. Are defined by a query joining one or more tables but marks them INVALID view are dropped as well the. Tables so that users can only see certain columns emp DROP constraint SYS_C00541121 ; table altered name... 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