Category: Relational

Understanding the WINDOW Clause in MySQL

Posted on by Ian

In MySQL, the WINDOW clause is an optional clause that we can use to create a named window. The named window can then be referred to from a window function.

Many SQL developers define their window functions directly in the OVER clause. But that’s not the only way to do it. We can also define them in a WINDOW clause, and then refer to them in the OVER clause.

When we define the window function in a WINDOW clause, we name it. When we do this, we can refer to that name from the OVER clause. This eliminates the need to include the definition directly inside the OVER clause.

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5 Ways to Fix Error 1364 “Field ‘…’ doesn’t have a default value” in MySQL

Posted on by Ian

If you’re getting MySQL error 1364, that reads something like Field 'column_name' doesn't have a default value, where column_name is the name of a column in your table, it’s probably because you’re trying to perform an operation that retrieves the column’s default value, but it doesn’t have a default value.

This can happen when the column is set to NOT NULL and hasn’t been defined with an explicit default value.

The solution to this issue will depend on what we’re trying to do. Below are examples of how to fix this error.

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Understanding the sys.quote_identifier() Function in MySQL

Posted on by Ian

In MySQL, we can use the sys.quote_identifier() function to quote a string to produce a result that can be used as an identifier in a SQL statement.

The string is returned enclosed by backticks (`), with each instance of a backtick doubled.

This function can be handy when a value to be used as an identifier is a reserved word or contains backtick characters.

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2 Ways to Add a DEFAULT Clause to an Existing Column in MySQL

Posted on by Ian

If you have an existing column in MySQL that you want to add a DEFAULT clause to, the following example may help.

To explicitly add a DEFAULT clause to an existing column in MySQL, we can use the ALTER TABLE statement along with the MODIFY clause.

We can also add a DEFAULT clause implicitly by defining a column as nullable. When we do this, MySQL implicitly adds its own DEFAULT clause.

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Fix Error 1138 “Invalid use of NULL value” in MySQL

Posted on by Ian

If you’re getting error 1138 that reads “invalid use of NULL value“, it could be because you’re trying to change the definition of a column to require non-NULL values, but the column contains NULL values.

This can happen when we try to change a column from NOT NULL to NULL. It can also happen when we try to set a column as a primary key, but that column contains NULL values.

To fix this issue, be sure to ensure that the column you’re modifying doesn’t contain any NULL values. Alternatively, if the column should be able to accept NULL values, then you should change your column definition to allow NULL values.

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