MySQL DROP TABLE Statement

Introduction

The DROP TABLE statement removes a table from a MySQL database. It deletes the entire structure and content of the table.

The tutorial explores the DROP statement commands and shows how to drop tables from MySQL databases.

Prerequisites

• Access to the terminal.
• A system running MySQL.
• A working database.
• A MySQL user with the necessary privileges (DROP privileges required).

MySQL DROP TABLE Syntax

To remove a table in MySQL, use the DROP TABLE statement. The basic command syntax is as follows:

DROP TABLE table_name;

The more extended syntax is:

DROP [TEMPORARY] TABLE [IF EXISTS] table_name [, table_name] [RESTRICT | CASCADE];

Let’s break down the syntax:

• The DROP TABLE statement deletes a table and its rows permanently.
• The [TEMPORARY] option ensures you remove temporary tables only.
• The [IF EXISTS] option drops a table only if it exists.
• The [RESTRICT] ensures a parent row is not deleted if a child row references a value in the said parent row.
• The [CASCADE] option ensures that when you delete a row, all rows in the related tables referencing the row are also deleted.

MySQL DROP TABLE Examples

There are several ways to delete a table in MySQL. The following text elaborates on them.

DROP a Table

To permanently remove a table, enter the following statement within the MySQL shell:

DROP TABLE table1;

The command deletes table1. Replace table1 with the name of the table you want to delete. When you delete a table, all the data contained in it is permanently removed along with the table structure.

DROP Existing Tables

MySQL generates an error if you try to drop a table that does not exist. This issue occurs when you include the DROP statement in a predefined script.

To check if a table exists, run the following command:

DROP TABLE IF EXISTS table1;

The IF EXISTS option generates a warning if table1 does not exist.

Using this option prevents a script from getting stuck on an error. Display the warning by entering:

SHOW WARNINGS;

The warning shows the table does not exist.

DROP Multiple Tables

To drop multiple tables with a single DROP statement, do the following:

DROP TABLE IF EXISTS table1, table2, table3;

The IF EXISTS option shows one warning as table1 does not exist. Other tables are deleted.

DROP a Temporary Table

Temporary tables are used to generate and store a data set shortly before using it.

For example, you might decide to store the results of a SELECT statement with multiple JOIN statements in a temporary table. Instead of repeating the entire query each time, query the temporary table directly.

To remove temporary tables without risking losing regular tables, use the TEMPORARY option:

DROP TEMPORARY TABLE IF EXISTS table4;

DROP Tables Based on Character Strings

MySQL does not have a built-in command to drop tables that match a string of characters. Instead, use a script to help perform this task. For example, you have a testdb database with three tables: temp_table1, temp_table2, and permanent_table.

The goal is to drop all tables in the testdb database whose names start with temp_. Take the following steps to do this:

1. Define the database and string of characters you want to filter:

set @schema = 'tableselection';
set @string = 'table%';

Replace tableselection with your database name. Replace table% with the string of characters you want to select and delete. Make sure to leave the % wildcard at the end.

In our example, it looks like this:

SET @schema = 'testdb'; 
SET @string = 'temp_%';

2. Create a MySQL statement to drop tables matching the pattern:

SELECT CONCAT('DROP TABLE ', GROUP_CONCAT(CONCAT(@schema, '.', table_name)), ';')
INTO @droptool
FROM information_schema.tables
WHERE table_schema = @schema
AND table_name LIKE @string;

This code consists of:

• The SELECT statement. Constructs a DROP TABLE command for all tables in the specified database that match the given pattern.
• The CONCAT functions. Builds the full table names and combines them into a single command.
  • The GROUP_CONCAT function. Combines the table names into a comma-separated list.
• The INTO @droptool clause. Stores the constructed command in the @droptool variable.
• The FROM information_schema.tables clause. Specifies the source of table information.
• The WHERE clauses. Filters the tables to match the specified database and name pattern.
  • WHERE table_schema = @schema. Ensures only tables from the specified database are considered.
  • AND table_name LIKE @string. Ensures only tables whose names match the specified pattern (e.g., starting with temp_) are included.

3. Create a selection from the code results:

SELECT @droptool;

The command retrieves and displays the @droptool variable contents. This step allows you to view the generated DROP TABLE statement before executing it.

4. Prepare and execute the generated DROP TABLE statement:

PREPARE stmt FROM @droptool;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

The command consists of:

• The PREPARE statement. Prepares the SQL statement stored in the @droptool variable. It sets up the command so it can be executed.
• The EXECUTE statement. Executes the DROP TABLE command, which deletes the specified tables.
• The DEALLOCATE statement. Frees up the resources associated with the prepared statement.

MySQL DROP TABLE vs. TRUNCATE

There are two ways to remove all data from the table: the DROP TABLE and TRUNCATE TABLE commands. However, they work differently and have different effects.

The DROP TABLE statement completely removes the table, including its structure and data. The TRUNCATE TABLE command deletes the data but leaves the structure.

TRUNCATE TABLE is especially useful if you want to delete a table and create a new table with the same structure. Instead of using DROP TABLE and CREATE TABLE, use TRUNCATE TABLE.

Conclusion

This tutorial explained how to use DROP TABLE to remove tables from a MySQL database. Additionally, the text elaborated on how to find and delete tables based on character strings.

Next, learn about the most important MySQL commands and how to use them in our MySQL commands cheat sheet.