Question

I have an MySQL Query looks like that:

SELECT
  client.id, client.vorname, client.nachname, DATE_FORMAT(geburtsDatum, '%d.%m.%Y'), zahlung.zuUebBet, zahlung.betrag
FROM
  zahlung JOIN client ON ( zahlung.mitgliedsNr = client.id )
WHERE
  client.typ = 'U'
OR
  client.typ is null
AND
  zahlung.typ = 'Beitrag'
AND
  anBGueberwiesen = '0000-00-00'
AND
  zahlung.zuUebBet IS NOT NULL
AND 
  (
    zahlung.vomBGeinheb = 0
  OR
    zahlung.vomBGeinheb is null
  )

All work fine but the case:

zahlung.zuUebBet IS NOT NULL

looks like beeing ignored. (I get rows with lots of NULL in it)

Anyone know whats going on?

Answer 1

please take a look at the operator precedence of mysql. OR has a lower precedence than AND, so you’ll have to put this into braces to get the desired result:

  client.typ = 'U'
OR
  client.typ is null

the complete WHERE-block should look like this:

  (
    client.typ = 'U'
  OR
    client.typ is null
  )
AND
  zahlung.typ = 'Beitrag'
AND
  anBGueberwiesen = '0000-00-00'
AND
  zahlung.zuUebBet IS NOT NULL
AND 
  (
    zahlung.vomBGeinheb = 0
  OR
    zahlung.vomBGeinheb is null
  )

otherwise, the sql-statement would be treated like the following (wich isn’t what you wanted, i think) (i’ve added braces to make things clear):

  client.typ = 'U'
OR
  (
    client.typ is null
  AND
    zahlung.typ = 'Beitrag'
  AND
    anBGueberwiesen = '0000-00-00'
  AND
    zahlung.zuUebBet IS NOT NULL
  AND 
    (
      zahlung.vomBGeinheb = 0
    OR
      zahlung.vomBGeinheb is null
    )
  )