How to Use MySQL INSERT Statement with IF Field Not Exists Condition

The MySQL INSERT statement is used to insert one or more rows into a table. However, sometimes you may want to add a column to the table only if it does not already exist. This can be achieved by using the IF field not exists condition in your INSERT statement.

In this tutorial, we will learn how to use the MySQL INSERT statement with an IF field not exists condition. We will also explore some examples and scenarios where this condition is useful.

Using IF Field Not Exists Condition

To add a column to a table only if it does not already exist, you can use the following syntax:

```sql

IF NOT EXISTS (SELECT * FROM information_schema.COLUMNS WHERE TABLE_SCHEMA=DATABASE() AND COLUMN_NAME='column_name' AND TABLE_NAME='table_name')

THEN

ALTER TABLE table_name ADD column_name datatype;

END IF;

```

Here, `column_name` is the name of the column you want to add, `datatype` is the data type of the column, and `table_name` is the name of the table where you want to add the column.

For example, let's say we have a table called `sale_details` with four columns: `id`, `name`, `email`, and `phone`. We want to add a new column called `sale_person_designation` with a VARCHAR data type only if it does not already exist in the table. The SQL statement would be:

```sql

IF NOT EXISTS (SELECT * FROM information_schema.COLUMNS WHERE TABLE_SCHEMA=DATABASE() AND COLUMN_NAME='sale_person_designation' AND TABLE_NAME='sale_details')

THEN

ALTER TABLE sale_details ADD sale_person_designation VARCHAR(255);

END IF;

```

When you execute this statement, MySQL will check if the column `sale_person_designation` already exists in the table `sale_details`. If it does not exist, then MySQL will add the column with the specified data type. If the column already exists, then nothing will happen.

Example Scenario

Let's say we have a procedure called `addColumnToTable` that adds a new column to a table only if it does not already exist. We can call this procedure whenever we want to run it:

```sql

DELIMITER $$

CREATE PROCEDURE IF NOT EXISTS addColumnToTable()

BEGIN

IF NOT EXISTS (SELECT * FROM information_schema.COLUMNS WHERE TABLE_SCHEMA=DATABASE() AND COLUMN_NAME='sale_person_designation' AND TABLE_NAME='sale_details')

THEN

ALTER TABLE sale_details ADD sale_person_designation VARCHAR(255);

END IF;

END $$

DELIMITER ;

```

To execute this procedure, you can use the following SQL statement:

```sql

CALL addColumnToTable();

```

When you call this procedure, MySQL will check if the column `sale_person_designation` already exists in the table `sale_details`. If it does not exist, then MySQL will add the column with the specified data type. If the column already exists, then nothing will happen.

In conclusion, using the IF field not exists condition in your MySQL INSERT statement allows you to add a column to a table only if it does not already exist. This can be useful when you want to avoid errors caused by duplicate column names or other issues. With this syntax, you can ensure that your database schema is consistent and up-to-date.

References

* MySQL documentation: 'https://dev.mysql.com/doc/refman/8.0/en/alter-table.html'(https://dev.mysql.com/doc/refman/8.0/en/alter-table.html)

* W3Schools: 'https://www.w3schools.com/sql/'(https://www.w3schools.com/sql/)

Mysql insert into if field not exists