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IF (condition)
    THEN
        true_statement
[ELSE]
    false_statement
END IF;

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¼ÙÉèÎÒÃÇÓÐÒ»¸öÃûΪ customers µÄ±í£¬ÆäÖаüÀ¨ÒÔÏÂÊý¾Ý£º

id name age
1 John Doe 30
2 Jane Smith 25
3 Peter Parker 18

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SELECT * FROM customers
WHERE age > 25;

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SELECT id, name,
    CASE
        WHEN age > 25 THEN 'Eligible for VIP discount'
        ELSE 'Not eligible for VIP discount'
    END AS eligibility
FROM customers;

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id name eligibility
1 John Doe Eligible for VIP discount
2 Jane Smith Not eligible for VIP discount
3 Peter Parker Not eligible for VIP discount

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IF Óï¾äÔÚ SQL Öл¹ÓÃÓÚ£º

¸üмͼ£ºUPDATE table_name SET column_name = value WHERE condition;

ɾ³ý¼Í¼£ºDELETE FROM table_name WHERE condition;

ÉèÖñäÁ¿£ºSET @variable_name = expression WHERE condition;

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