1
if 条件:
2
  子代码
3
elif 条件:
4
  子代码
5
else:
6
  子代码

1
if(条件){
2
  子代码
3
}else if(条件){
4
  子代码
5
}else{
6
  子代码
7
}

1
if 条件 then
2
      子代码
3
elseif 条件 then
4
      子代码
5
else
6
      子代码
7
end if;

1
DECLARE num INT ;
2
SET num = 0 ;
3
WHILE num < 10 DO
4
  SELECT num ;
5
  SET num = num + 1 ;
6
END WHILE ;

1
IF condition THEN
2
    statements;
3
ELSE
4
    statements;
5
END IF;

1
SELECT
2
    IFNULL(Bonus, 0) AS Bonus
3
FROM
4
    Employees;

1
CASE expression
2
    WHEN value1 THEN
3
        statements;
4
    WHEN value2 THEN
5
        statements;
6
    ...
7
    ELSE
8
        statements;
9
END CASE;

1
CASE
2
    WHEN condition1 THEN
3
        statements;
4
    WHEN condition2 THEN
5
        statements;
6
    ...
7
    ELSE
8
        statements;
9
END CASE;

1
SELECT
2
    CASE
3
        WHEN Salary > 5000 THEN 'High'
4
        ELSE 'Low'
5
    END AS SalaryGroup,
6
    COUNT(*) AS EmployeeCount
7
FROM
8
    Employees
9
GROUP BY
10
    SalaryGroup;

1
WHILE condition DO
2
    statements;
3
END WHILE;

1
SET i = 1;
2
WHILE i <= 5 DO
3
    SELECT CONCAT('The number is: ', i) AS Number;
4
    SET i = i + 1;
5
END WHILE;

1
LOOP
2
    statements;
3
    IF condition THEN
4
        LEAVE;
5
    END IF;
6
END LOOP;

1
SET i = 1;
2
LOOP
3
    SELECT CONCAT('The number is: ', i) AS Number;
4
    SET i = i + 1;
5
    IF i > 10 THEN
6
        LEAVE;
7
    END IF;
8
END LOOP;

1
FOR var IN start, increment, end DO
2
    statements;
3
END FOR;

1
SET i = 1;
2
FOR j IN 1, 2, 6 DO
3
    SELECT CONCAT('The number is: ', i) AS Number;
4
    SET i = i * j;
5
END FOR;

1
DELIMITER //
2
CREATE PROCEDURE proc_if()
3
BEGIN
4
    DECLARE i INT DEFAULT 0;
5
    IF i = 1 THEN
6
        SELECT 1;
7
    ELSEIF i = 2 THEN
8
        SELECT 2;
9
    ELSE
10
        SELECT 7;
11
    END IF;
12
END //
13
DELIMITER ;

1
DELIMITER //
2
CREATE PROCEDURE proc_while()
3
BEGIN
4
    DECLARE num INT DEFAULT 0;
5
    WHILE num < 10 DO
6
        SELECT num;
7
        SET num = num + 1;
8
    END WHILE;
9
END //
10
DELIMITER ;