Question

I am trying to work out how SQL queries are run and have hit a bit of a stumbling block.

If a where clause akin to the below is used:

A OR B AND C

This could mean either of the below

(A OR B) AND C

or

A OR (B AND C)

In the majority of cases the results will be the same, but if the set to be queried contains solely {A}, the first variant would return an empty result set and the second would return {A}. SQL does in fact return the 1 result.

Does anyone know (or have links to) any insight that will help me understand how queries are built?

Ketchup

Answer 1

The order is the following according to MSDN:

1. ~ (Bitwise NOT)

2. (*) (Multiply), / (Division), % (Modulo)

3. (+) (Positive), – (Negative), + (Add), (+ Concatenate), – (Subtract), & (Bitwise AND), ^ (Bitwise Exclusive OR), | (Bitwise OR)

4. =, >, <, >=, <=, <>, !=, !>, !< (Comparison operators)

5. NOT

6. AND

7. ALL, ANY, BETWEEN, IN, LIKE, OR, SOME

8. = (Assignment)