2015-12-12 15:24 GMT+01:00 R Smith <rsmith at rsweb.co.za>: > > > On 2015/12/12 4:18 PM, Cecil Westerhof wrote: > >> ?I have the following query: >> SELECT >> (SELECT COUNT(*) FROM proverbs) AS Total >> , (SELECT COUNT(*) FROM proverbs WHERE NOT used IS NULL) AS Used >> >> But I want something like: >> ? SELECT >> (SELECT COUNT(*) FROM proverbs) AS Total >> , (SELECT COUNT(*) FROM proverbs WHERE NOT used IS NULL) AS Used >> , (Total - Used) AS Free >> > > SELECT > (SELECT COUNT(*) FROM proverbs) AS Total > , (SELECT COUNT(*) FROM proverbs WHERE used IS NOT NULL) AS Used > , (SELECT COUNT(*) FROM proverbs WHERE used IS NULL) AS Free >
?That is what I am using now, but it is inefficient. This uses three scans instead of two.? -- Cecil Westerhof
