Postgres 7.3 User's Guide
5.12. Arrays

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SELECT * FROM sal_emp WHERE pay_by_quarter[1:4] *= 10000;
To search the entire array (not just specified columns), you could use:

SELECT * FROM sal_emp WHERE pay_by_quarter *= 10000;
In addition, you could find rows where the array had all values equal to 10 000 with:

SELECT * FROM sal_emp WHERE pay_by_quarter **= 10000;