CASE: WHEN column1 IS NULL THEN write column2

Is it possible to show data from another column if checked column IS NULL?

For example:

• Columns: Color, OriginalColor

• Table: TableColors [Color, OriginalColor]

  [W, B] [ , G] [B, Y]

And the

SELECT CASE WHEN Color IS NULL "extract the data from Or开发者_开发知识库iginalColor"
FROM TableColors

should get following list: W, G, B

Could you be looking for COALESCE? The function return the first non-NULL value.

SELECT COALESCE(`Color`, `OriginalColor`) AS `Color` FROM `TableColors`;

Check out coalesce - http://www.roseindia.net/sql/mysql-example/mysql-coalesce.shtml

The documentation is quite clear about this:

• CASE statement http://dev.mysql.com/doc/refman/5.5/en/case-statement.html
• IF function http://dev.mysql.com/doc/refman/5.5/en/control-flow-functions.html#function_if
• IFNULL function http://dev.mysql.com/doc/refman/5.5/en/control-flow-functions.html#function_ifnull
• COALESCE function http://dev.mysql.com/doc/refman/5.5/en/comparison-operators.html#function_coalesce

The IFNULL() function might be the easiest solution to your problem

SELECT
CASE
WHEN Color IS NULL THEN OriginalColor
ELSE Color
END  AS Color_Or_OriginalColor
FROM TableColors

Edit: one of the many possible ways.