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<chapter id="query">

As an example, say we wish to find all the records that

are in the temperature range of other records. In

effect, we need to compare the temp_lo and temp_hi

attributes of eachEMP instance to the temp_lo and

temp_hi attributes of all otherEMP instances.

attributes of eachWEATHER instance to the temp_lo and

temp_hi attributes of all otherWEATHER instances.

<note>

<para>

This is only a conceptual model. The actual join may

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Postgres documentation

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CREATE RULE bad_rule_combination_1 AS

ON SELECT TO emp

DO INSTEAD

SELECTTO toyemp;

SELECT* FROM toyemp;

</programlisting>

<programlisting>

CREATE RULE bad_rule_combination_2 AS

ON SELECT TO toyemp

DO INSTEAD

SELECTTO emp;

SELECT* FROM emp;

</programlisting>

<para>

This attempt to select from EMP will cause