
 Description
 
 Tests whether the table specified in in_db and in_table exists either as a regular
 table, or as a temporary table. The returned value corresponds to the table that
 will be used, so if there's both a temporary and a permanent table with the given
 name, then 'TEMPORARY' will be returned.
 
 Parameters
 
 in_db (VARCHAR(64)):
 The database name to check for the existance of the table in.
 
 in_table (VARCHAR(64)):
 The name of the table to check the existance of.
 
 out_exists ENUM('', 'BASE TABLE', 'VIEW', 'TEMPORARY'):
 The return value: whether the table exists. The value is one of:
 * ''           - the table does not exist neither as a base table, view, nor temporary table.
 * 'BASE TABLE' - the table name exists as a permanent base table table.
 * 'VIEW'       - the table name exists as a view.
 * 'TEMPORARY'  - the table name exists as a temporary table.
 
 Example
 
 mysql> CREATE DATABASE db1;
 Query OK, 1 row affected (0.07 sec)
 
 mysql> use db1;
 Database changed
 mysql> CREATE TABLE t1 (id INT PRIMARY KEY);
 Query OK, 0 rows affected (0.08 sec)
 
 mysql> CREATE TABLE t2 (id INT PRIMARY KEY);
 Query OK, 0 rows affected (0.08 sec)
 
 mysql> CREATE view v_t1 AS SELECT * FROM t1;
 Query OK, 0 rows affected (0.00 sec)
 
 mysql> CREATE TEMPORARY TABLE t1 (id INT PRIMARY KEY);
 Query OK, 0 rows affected (0.00 sec)
 
 mysql> CALL sys.table_exists('db1', 't1', @exists); SELECT @exists;
 Query OK, 0 rows affected (0.00 sec)
 
 +------------+
 | @exists    |
 +------------+
 | TEMPORARY  |
 +------------+
 1 row in set (0.00 sec)
 
 mysql> CALL sys.table_exists('db1', 't2', @exists); SELECT @exists;
 Query OK, 0 rows affected (0.00 sec)
 
 +------------+
 | @exists    |
 +------------+
 | BASE TABLE |
 +------------+
 1 row in set (0.01 sec)
 
 mysql> CALL sys.table_exists('db1', 'v_t1', @exists); SELECT @exists;
 Query OK, 0 rows affected (0.00 sec)
 
 +---------+
 | @exists |
 +---------+
 | VIEW    |
 +---------+
 1 row in set (0.00 sec)
 
 mysql> CALL sys.table_exists('db1', 't3', @exists); SELECT @exists;
 Query OK, 0 rows affected (0.01 sec)
 
 +---------+
 | @exists |
 +---------+
 |         |
 +---------+
 1 row in set (0.00 sec)
 