3 table sql join

I need to join tableA, tableB, and tableC, but it's possible that tableB won't have a corresponding row. Posted below is ho开发者_高级运维w I am currently doing the query. The problem with it is that if tableB doesn't have a correspoinding row, it won't return a result. My sql skills are very rusty so I appreciate your help. Thanks.

SELECT [column names]
FROM tableA AS a, tableB AS b, tableC as c
WHERE b.blah = a.blah
AND c.foo = a.foo
AND [more where conditions]

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Don't use the , syntax. Use JOIN to allow for a readable LEFT JOIN...

SELECT
  *
FROM
  tableA
LEFT JOIN
  tableB
    ON TableB.x = TableA.y
LEFT JOIN
  tableC
    ON TableC.x = TableB.y
    AND TableC.y = TableA.z

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Use a LEFT JOIN.

SELECT [column names]
FROM 
    tableA AS a 
    LEFT JOIN tableB AS b ON b.blah = a.blah
    JOIN tableC as c ON c.foo = a.foo

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SELECT [column names]
FROM tableA AS a INNER JOIN tableC as c ON (c.foo = a.foo)
LEFT OUTER JOIN tableB as B on (b.blah = a.blah)
WHERE [more where conditions]

If the [more where conditions] are on B, then you need to include them in the OUTER JOIN ON clause.

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The terminology here (so you can look up more details) is an Outer Join. The other answer(s) are fine -- but watch out for whether you want an INNER or OUTER join on table c (do you want records returned if there are no matching rows in tableC)? Here is a link for the general issue.

http://www.w3schools.com/sql/sql_join_left.asp