I have a table with three columns:
ColumnA ColumnB ColumnC
AAA NULL 123
BBB 222 NULL
CCC NULL NULL
I would like to create a SELECT statement which will return ColumnA, and then a second column which will either show the value of ColumnB unless ColumnB is null; otherwise it will show the value of ColumnC, even it it's NULL. Can I use an IF statement for that? Something like:
SELECT ColumnA,
IF(ColumnB IS NULL, ColumnC, ColumnB)
FROM tab开发者_开发问答le
**If I get this working, the next step would be to return the value of a joined column instead of ColumnB. In effect the IF statement would be
IF(table.ColumnB IS NULL, table.ColumnC, table2.ColumnD)
Use COALESCE
SELECT ColumnA, COALESCE(ColumnB, ColumnC) as 'Value'
Reading to the end of your question it sounds like you need to use CASE
CASE WHEN table.ColumnB IS NULL
THEN table.ColumnC
ELSE table2.ColumnD
END AS Whatever
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