![]() ![]() There is no defined maximum for the number of WHEN conditions you can have within a CASE WHEN statement. Time to complete a query can be a problem. Note: you do not have to show all of the columns, or any columns besides the CASE column in the output. SELECT ( optional : any desired columns ), CASE WHEN ( condition ) THEN ( desired output ) WHEN ( other condition ) THEN ( desired output ) ELSE ( desired output ) END AS ( descriptive header for the output column ) FROM ( appropriate table ) In the example we see this done with ELSE City which puts LA unchanged in the new column Syntax NOTE: If you put the column name after THEN or ELSE it will put the value from the original column into the newly created column. AS: Used to set a specific name for the returned CASE column. ![]() END: Indicates the end of the CASE loop.If no ELSE statement is present and all WHEN conditions are false, the returned value will be NULL.ELSE: catches all of the entries that were not true for any of the WHEN conditions.If the condition is false, the next WHEN statement will be evaluated.After THEN is executed, CASE will return to the top of the loop and begin checking the next entry.THEN: executed when the condition is true, determines the output for the true condition.WHEN: indicates the start of a condition that should be checked by the query.CASE: indicates a condition loop has been started and that the conditions will follow.Let’s break down each component of the CASE WHEN statement: SELECT City, CASE WHEN City = "SF" THEN "San Francisco" ELSE City END AS "Updated City" FROM friends ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |