MySQL INSERT IGNORE Statement Explained?

Summary: in this tutorial, you will learn how to use the MySQL INSERT IGNORE statement to insert data into a table.

Introduction to MySQL INSERT IGNORE statement

When you use the INSERT statement to add some rows to a table and if an error occurs during the processing, MySQL will abort the INSERT statement and return an error. As the result, no rows are inserted into the table.

However, if you use the INSERT IGNORE statement, the rows that cause the errors are ignored and the remaining rows are inserted into the table.

The syntax of the INSERT IGNORE statement is as follows:

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INSERT IGNORE INTO table(column_list) VALUES( value_list),       ( value_list),       ...

Note that the IGNORE clause is an extension of MySQL to the SQL standard.

MySQL INSERT IGNORE example

We will create a new table called subscribers for the demonstration.

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CREATE TABLE subscribers (     id INT PRIMARY KEY AUTO_INCREMENT,     email VARCHAR(50) NOT NULL UNIQUE );

The UNIQUE constraint ensures that no duplicate email exists in the email column.

The following statement inserts a new row into the  subscribers table:

1 2	INSERT INTO subscribers(email) VALUES('john.doe@gmail.com');

It worked as expected.

Let’s execute another statement that inserts two rows into the  subscribers table:

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INSERT INTO subscribers(email) VALUES('john.doe@gmail.com'),       ('jane.smith@ibm.com');

It returns an error.

1	Error Code: 1062. Duplicate entry 'john.doe@gmail.com' for key 'email'

As indicated in the error message, the email john.doe@gmail.com violates the UNIQUE constraint.

However, if you use the INSERT IGNORE statement instead.

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INSERT IGNORE INTO subscribers(email) VALUES('john.doe@gmail.com'),       ('jane.smith@ibm.com');

MySQL returned a message indicating that one row was inserted and the other row was ignored.

1	1 row(s) affected, 1 warning(s): 1062 Duplicate entry 'john.doe@gmail.com' for key 'email' Records: 2  Duplicates: 1  Warnings: 1

To find the detail of the warning, you can use the SHOW WARNINGS command as shown below:

1	SHOW WARNINGS;

In conclusion, when you use the INSERT IGNORE statement, instead of issuing an error, MySQL issued a warning in case an error occurs.

If you query data from subscribers table, you will find that only one row was actually inserted and the row that causes the error was not.

MySQL INSERT IGNORE and STRICT Mode

When the strict mode is on, MySQL returns an error and aborts the INSERT statement if you try to insert invalid values into a table.

However, if you use the INSERT IGNORE statement, MySQL will issue a warning instead of an error. In addition, it will try to adjust the values to make them valid before adding the value to the table.

Consider the following example.

First, we create a new table named tokens:

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CREATE TABLE tokens (     s VARCHAR(6) );

In this table, the column s accepts only string whose lengths are less than or equal to six.

Second, insert a string whose length is seven into the tokens table.

1	INSERT INTO tokens VALUES('abcdefg');

MySQL issued the following error because the strict mode is on.

1	Error Code: 1406. Data too long for column 's' at row 1

Third, use the INSERT IGNORE statement to insert the same string.

1	INSERT IGNORE INTO tokens VALUES('abcdefg');

MySQL truncated data before inserting it into the tokens table. In addition, it issues a warning.

In this tutorial, you have learned how to use the MySQL INSERT IGNORE statement to insert rows into a table and ignore error for rows that cause errors.