How exists works in Oracle?
The Oracle EXISTS condition is used in combination with a subquery and is considered “to be met” if the subquery returns at least one row. … It can be used in a SELECT, INSERT, UPDATE, or DELETE statement.
How do I check if a table exists in PL SQL?
You can also check the data dictionary to see if a table exists: SQL> select table_name from user_tables where table_name=’MYTABLE’; Another way to test if a table exists is to try to drop the table and catch the exception if it does not exist.
What is the use of exists operator?
The EXISTS operator is used to test for the existence of any record in a subquery. The EXISTS operator returns TRUE if the subquery returns one or more records.
How do you use exists and not exists in Oracle?
Introduction to the Oracle NOT EXISTS operator
The NOT EXISTS operator works the opposite of the EXISTS operator. We often use the NOT EXISTS operator with a subquery to subtract one set of data from another. The NOT EXISTS operator returns true if the subquery returns no row. Otherwise, it returns false.
Which is faster in or exists in Oracle?
The EXISTS clause is much faster than IN when the subquery results is very large. Conversely, the IN clause is faster than EXISTS when the subquery results is very small. Also, the IN clause can’t compare anything with NULL values, but the EXISTS clause can compare everything with NULLs.
How do you check if a table is empty in Oracle?
IF((SELECT COUNT(*) FROM IPA_PRCADJ_HDR WHERE TRM_CODE = 41) = 0) THEN select ‘111111’ from dual; ELSE SELECT ‘0000000’ FROM DUAL; END IF; showing error..
How do you create a table only if it does not exist in Oracle?
Oracle CREATE TABLE IF NOT EXISTS Equivalent
- You can attempt to create a table, and catch the error that appears (ORA-00955: name is already in use by an existing object).
- You can query the USER_TABLES view to find a count where the table name matches, and check if the value is > 0.
How do you check if data exists in a table in Oracle?
Check if record exists using the Count() function
The following Oracle PL/SQL block will use the count() function in implicit cursor to count the records for particular criteria. If the count is greater than 0 means, the records exist else not exist.
How do you use exists?
The EXISTS condition in SQL is used to check whether the result of a correlated nested query is empty (contains no tuples) or not. The result of EXISTS is a boolean value True or False. It can be used in a SELECT, UPDATE, INSERT or DELETE statement.
Does not exist SQL?
The SQL NOT EXISTS Operator will act quite opposite to EXISTS Operator. It is used to restrict the number of rows returned by the SELECT Statement. The NOT EXISTS in SQL Server will check the Subquery for rows existence, and if there are no rows then it will return TRUE, otherwise FALSE.
What is the difference between not in and not exists?
not in can also take literal values whereas not exists need a query to compare the results with. EDIT: not exists could be good to use because it can join with the outer query & can lead to usage of index, if the criteria uses column that is indexed.