Mysql drop table if not exist

MySQL: DROP TABLE Statement - techonthenet. For years nobody mentioned one subtle thing. Using ALTER to drop a column if it exists.

If any tables named in the argument list do not exist , DROP TABLE behavior depends on whether the IF EXISTS clause is given: Without IF EXISTS , the statement drops all named tables that do exist ,. With IF EXISTS , no error occurs for nonexisting tables. This is to ensure that the object to be dropped no longer exists on either the master or the slave, once the slave has caught up with the master. That will drop the table only if it contains any rows (and will raise an error if the table does not exist ). Using the command: CREATE TABLE IF NOT EXISTS `test`.

This is mostly uses to suppress error messages in the database schema creation scripts when they are executed for the first time. The IF EXISTS option conditionally drop a table only if it exists. Bugfix documented in the 5. When using row-based replication, DROP TEMPORARY TABLE IF EXISTS was written to the binary log if the table named in the statement did not exist , even though DROP TEMPORARY TABLE statement should never be logged in row-based mode, whether the table exists or not. The user who is using the DROP comman must have DROP privilege for each table (s) he wants to drop. The command removes all the data and table definition from the database.

MySQL has a built-in modifier for this. Let’s walk-through with few examples of important database objects to see how we can use DROP IF EXISTS option effectively. In the following example, the first statement will check if a table named Test exists in the tempdb database. If it does exists then it will try to DROP the table.

So, let’s first check the details and see how to use the DROP command. But first, create a sample table which we’ll use in our example. Description: It would be nice if the use of IF EXISTS did not cause a warning if the table does not exist. I like the second better. As I have mentioned earlier, IF EXISTS in DROP statement can be used for several objects.

In this article, I will provide examples of dropping objects like database, table , procedure, view and function, along with dropping columns and constraints. To prevent an error from occurring if you delete a database that does not exist , you can use the IF EXISTS option. The DROP DATABASE statement returns the number of tables that were deleted. SELECT NULL FROM information_schema. TABLES WHERE TABLE _SCHEMA=DATABASE() AND TABLE _NAME=?

If this returns no rows, then your table does not exist. This means that an INSERT IGNORE statement which contains a duplicate value in a UNIQUE index or PRIMARY KEY field does not produce an error, but will instead simply ignore that particular INSERT command entirely. The last three steps test the new default constraint.

Drop sequence object if it exists. Create new sequence object. Drop default constraint if it exists. Restart sequence value. Insert data into table.