TABLE_EXISTS Function
The task is fairly simple, create a function that takes two arguments and queries the OBJECTS system view and returns 1 for table exists and 0 for table doesn't exist.
Listing 1
CREATE FUNCTION TABLE_EXISTS(IN schema_name VARCHAR(256), IN table_name VARCHAR(256))
RETURNS exists int
AS
BEGIN
DECLARE _exists int := 0;
SELECT
CASE WHEN COUNT(*) > 0 THEN
1
ELSE
0
END INTO _exists
FROM OBJECTS WHERE OBJECT_TYPE='TABLE' AND SCHEMA_NAME=:schema_name AND OBJECT_NAME=:table_name;
exists = :_exists;
END;
As you can see in listing 1, the function takes two varchar arguments. The first is the schema name and the second is the table name. The select statement queries the system OBJECTS view using the schema and table name. I've added an additional condition to ensure the object type is a table.
The function above can be used to test if a table exists in any specified schema. If you want to test if a table exists in the current schema then use the CURRENT_SCHEMA function as shown in listing 2 below.
Listing 2
CREATE FUNCTION TABLE_EXISTS(IN table_name VARCHAR(256))
...
FROM OBJECTS WHERE OBJECT_TYPE='TABLE' AND SCHEMA_NAME=CURRENT_SCHEMA AND OBJECT_NAME=:table_name;
...
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