You probably never have to use the REPLACE SQL statement. It’s a system-specific extension to the standard SQL language used with MySQL databases and other similar systems.

REPLACE lets you modify your database records by replacing the current records with new ones. Its syntax looks very similar to the syntax of the INSERT command statement.

REPLACE INTO table_name (column list) VALES (column values);

Column list and column values are comma-separated lists of your table column names and your record’s data respectively. Like with INSERT, the column list is optional, but you will have to explicitly include values for every column in the table in the values list in their proper order.

REPLACE INTO company VALUES (2, NOW(), NOW(), ‘Joe\’s Steak House’);

The REPLACE SQL statement does two things. It first checks to see if the record you want replaced already exists in the table. If it finds a match, the statement deletes the old record and then inserts the new record information in its place. It adds a new record if it can’t find anything.

As you can see, the REPLACE SQL statement is a DELETE statement and an INSERT statement in a single SQL statement. In fact, you need both the INSERT and DELETE privilege in order to even use REPLACE.

You might be asking why you would ever need such statement, especially if you can just use the UPDATE statement instead. The answer lies in copying one table to another.

As a database, MySQL is the leader in web application database solutions. Its simple streamlined processes make it best for these high volume, high performance environments.  However, most good programmers test their programs on test platforms before they make them public. This means your company’s database may have test table set aside for these development tests. If your new website software needs be tested on live data, you can use the REPLACE statement to copy data from your production table to your test table without additional work. You just use the appropriate SELECT statement as the column values list.

REPLACE INTO test_table VALUES SELECT * FROM products_table;

You can even use the REPLACE SQL function inside the embedded SELECT statement.

REPLACE INTO test_table VALUES SELECT *, REPLACE(Region_name, ‘ast’, ‘astern’) FROM company_network;

In either case, the REPLACE SQL keyword signifies that something is being replaced with something else. You may never have to use either forms, but you should never confuse the two. The REPLACE SQL statement works like an INSERT statement with built-in validation checks. The REPLACE SQL function transforms a string into a new one by replacing a substring with another string. Both exist to make your database development as simple as possible.

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