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PostgreSQL documentation

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<replaceable class="parameter">query</replaceable>

|

( <replaceable class="parameter">query</replaceable> ; <replaceable class="parameter">query</replaceable> ... )

|

[ <replaceable class="parameter">query</replaceable> ; <replaceable class="parameter">query</replaceable> ... ]

</synopsis>

<refsect2 id="R2-SQL-CREATERULE-1">

</para>

<para>

The <replaceable class="parameter">action</replaceable> part of the rule

can consist of one or more queries.To write multiple queries, surround

them witheitherparentheses or square brackets.Such queries will be

performed in thespecified order (whereas there are no guarantees about

the executionorder of multiple rules for an object).The

<replaceableclass="parameter">action</replaceable> can also be NOTHING

indicatingno action.Thus, a DO INSTEAD NOTHING rule suppresses the

originalquery from executing (when its condition is true); a DO NOTHING

ruleis useless.

The <replaceable class="parameter">action</replaceable> part of the

rulecan consist of one or more queries. To write multiple queries,

surroundthem with parentheses.Such queries will be performed in the

specified order (whereas there are no guarantees about the execution

order of multiple rules for an object). The <replaceable

class="parameter">action</replaceable> can also be NOTHING indicating

no action. Thus, a DO INSTEAD NOTHING rule suppresses the original

query from executing (when its condition is true); a DO NOTHING rule

is useless.

</para>

<para>

RuleActionList:NOTHING{$$ = NIL; }

|RuleActionStmt{$$ = makeList1($1); }

|'['RuleActionMulti']'{$$ =$2; }

|'('RuleActionMulti')'{$$ =$2; }

;

RuleActionList:NOTHING {$$ = make_str("nothing"); }

|RuleActionStmt {$$ =$1; }

|'['RuleActionMulti']' {$$ = cat_str(3, make_str("["),$2, make_str("]")); }

|'('RuleActionMulti')' {$$ = cat_str(3, make_str("("),$2, make_str(")")); }

;