SQL · Theory

IF Statement

Theory

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IF Statement

Inside procedures: IF marks < 40 THEN SET msg = 'fail'; ELSE SET msg = 'pass'; END IF; This is not the IF() function. You need BEGIN … END and DELIMITER when creating the procedure.

Trap — writing IF THEN in a normal query tab. That’s a syntax error. Use IF() or CASE in SELECT.

On the example next to this theory: IF Statement: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Exam tip

IF THEN is for procedures. SELECT uses IF() / CASE.

IF Statement — sample query

-- IF Statement
CREATE TABLE demo (
  id INTEGER PRIMARY KEY,
  label TEXT NOT NULL,
  qty INTEGER DEFAULT 0
);
INSERT INTO demo (id, label, qty) VALUES
  (1, 'alpha', 2),
  (2, 'beta', 5);
SELECT label, qty FROM demo WHERE qty >= 2 ORDER BY qty DESC;

IF Statement: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Short notes

DefProcedural IF THEN END IF only in stored programs.
RuleSELECT uses IF() or CASE, not IF THEN.
TrapIF THEN in a normal query.

-- IF Statement CREATE TABLE demo ( id INTEGER PRIMARY KEY, label TEXT NOT NULL, qty INTEGER DEFAULT 0 ); INSERT INTO demo (id, label, qty) VALUES (1, 'alpha', 2), (2, 'beta', 5); SELECT label, qty FROM demo WHERE qty >= 2 ORDER BY qty DESC;

IF Statement

IF Statement — sample query

Short notes

Questions

IF Statement

IF Statement — sample query

Short notes

Questions