Make sure that you are comparing the correct data types in your queries. More on optimizing queries from Data School here. If queries are taking a long time to finish, consider finding ways to optimize your query. This can dramatically increase the query time. CASE WHEN queries can become very slow because the query has to check each condition for every row until it finds a case where it satisfies the condition. 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.
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