PostgreSQL - Triggers in PostgreSQL
Why does this BEFORE INSERT trigger cause an error? CREATE TRIGGER trg BEFORE INSERT ON tbl FOR EACH ROW EXECUTE FUNCTION trg_func();
Why does this BEFORE INSERT trigger cause an error? CREATE TRIGGER trg BEFORE INSERT ON tbl FOR EACH ROW EXECUTE FUNCTION trg_func();
medium📝 Debug Q7 of 15
Step-by-Step Solution
Solution:
Step 1: Validate trigger syntax
The syntax is correct for a BEFORE INSERT trigger with FOR EACH ROW.Step 2: Check trigger function existence
If trg_func() is not created or defined, PostgreSQL raises an error when creating or firing the trigger.Final Answer:
The trigger function trg_func() is missing or not defined -> Option AQuick Check:
Trigger function must exist before creating trigger [OK]
Quick Trick: Always create trigger function before creating trigger [OK]
Common Mistakes:
- Assuming BEFORE triggers can't be on INSERT
- Thinking FOR EACH ROW is invalid here
- Believing trigger name restrictions cause error
Master "Triggers in PostgreSQL" in PostgreSQL
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