如何使用条件从SQL中的另一个表更新列？

Question

我有2张桌子。

表1

CATEGORY | RANGE    | PERCENTAGE
 REG     | 250001   | 50
 REG     | 500001   | 40
 REG     | 9999999  | 30
 VIP     | 5001     | 50
 VIP     | 10001    | 40
 VIP     | 9999999  | 30

表2

CATEGORY | PRICE    | DISCOUNT
 REG     | 100000   |  0
 REG     | 400000   |  0
 REG     | 600000   |  0
 VIP     | 3000     |  0
 VIP     | 6000     |  0
 VIP     | 120000   |  0

 我想根据DISCOUNT和table 2 RANGE PERCENTAGE更新table 1中的WHEN PRICE is <= 250001 DISCOUNT = PRICE * 50% WHEN PRICE is > 250001 AND <= 500001 DISCOUNT = PRICE * 40% WHEN PRICE is > 500001 DISCOUNT = PRICE * 30%

CATEGORY REG

WHEN PRICE is  <= 5001 
DISCOUNT = PRICE * 50% 
WHEN PRICE is  > 10001 AND <= 500001
DISCOUNT = PRICE * 40% 
WHEN PRICE is  > 100001
DISCOUNT = PRICE * 30%

CATEGORY VIP

caused by: org.postgresql.util.PSQLException: ERROR: invalid memory alloc request size 1199606566
  Where: PL/pgSQL function if_modified_func() line 51 at assignment
SQL statement "INSERT INTO  logged_actions VALUES (audit_row.*)"
PL/pgSQL function if_modified_func() line 58 at SQL statement
SQL statement "INSERT INTO  logged_actions VALUES (audit_row.*)"
PL/pgSQL function if_modified_func() line 58 at SQL statement
SQL statement "INSERT INTO  logged_actions VALUES (audit_row.*)"
PL/pgSQL function if_modified_func() line 58 at SQL statement
SQL statement "INSERT INTO  logged_actions VALUES (audit_row.*)"
PL/pgSQL function if_modified_func() line 58 at SQL statement
SQL statement "INSERT INTO  logged_actions VALUES (audit_row.*)"
PL/pgSQL function if_modified_func() line 58 at SQL statement

Answer 1

试试这个：

UPDATE table2 t2 SET 
DISCOUNT = (
    SELECT max(t1.`percentage`) * t2.price / 100 FROM table1 t1
    WHERE
        t1.category = t2.category AND
        t2.price < t1.`range`
)

Answer 2

请尝试以下查询“REG”类别。您可以根据您的要求更改WHEN子句中的类别和条件。

UPDATE table2 
SET discount = CASE 
    WHEN price <= 250001 THEN ((price*50)/100)
    WHEN (price BETWEEN 250002 AND 500001) THEN ((price*40)/100)
    WHEN price > 500001 THEN ((price*30)/100)
    ELSE discount 
END
WHERE category = 'REG'

检查类别'REG'的更新查询：

UPDATE table2 SET discount = 
(SELECT ((price*a.percentage)/100) FROM table1 as a WHERE price <= a.range AND category='REG' LIMIT 1) 
WHERE category = 'REG'

检查以下查询（编辑＃2）：

UPDATE table2 AS b SET discount = 
(SELECT ((b.price*a.percentage)/100) FROM table1 as a WHERE a.range >= b.price AND a.category=b.category LIMIT 1)

确保引用范围列，因为range是MYSQL保留关键字。另请注意，range列的数据类型应为整数。