For example, SELECT x, y + z FROM t
is allowed but
UNION ALL
SELECT x, y + z FROM t
ORDER BY y + zSELECT x, y, z FROM t
UNION ALL
SELECT x, y, z FROM t
ORDER BY y + zSELECT x, y, z FROM t ORDER BY y + z
is not.
Access is an example of a dialect with this restriction. @return whether this dialect allows an expression in the ORDER BYclause of a UNION (or other set operation) query only if it occurs in the SELECT clause
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