[英]UPDATE and SELECT from same table in one query
我正在尝试计算table1中的行,并根据行数来更新特定的列。 以下是我尝试过的查询,但收到一个错误消息,说temp不是表。
UPDATE table1 AS t1
INNER JOIN table1 AS temp ON temp.id = t1.id
SET
t1.field1 = (CASE
WHEN (SELECT COUNT(*) FROM temp WHERE temp.field1 = 1) < 100 THEN 1
WHEN (SELECT COUNT(*) FROM temp WHERE temp.field1 = 2) < 100 THEN 2
WHEN (SELECT COUNT(*) FROM temp WHERE temp.field1 = 3) < 100 THEN 3
WHEN (SELECT COUNT(*) FROM temp WHERE temp.field1 = 4) < 100 THEN 4
WHEN (SELECT COUNT(*) FROM temp WHERE temp.field1 = 5) < 100 THEN 5
END)
WHERE t1.id IN(100, 200, 300); --Example data
几件事:
我建议在您的case语句中创建一个数据临时表,然后将其加入以进行更新。
重新加入要更新的表无法正常工作。
您的where子句中有语法错误。 IN之前不需要等号。
尝试:
DROP TABLE IF EXISTS temp_table1;
CREATE TEMPORARY TABLE temp_table1 AS
SELECT field1,count(*) as field_count FROM table1 group by field1;
UPDATE table1 AS t1
LEFT JOIN temp_table1 aa
ON aa.field1= t1.field1
SET t1.field1 = (CASE
WHEN aa.field1 = 1 AND aa.field_count < 100 THEN 1
WHEN aa.field1 = 2 AND aa.field_count < 100 THEN 2
WHEN aa.field1 = 3 AND aa.field_count < 100 THEN 3
WHEN aa.field1 = 4 AND aa.field_count < 100 THEN 4
WHEN aa.field1 = 5 AND aa.field_count < 100 THEN 5 END)
WHERE t1.id IN (100, 200, 300);
以下查询将对您有所帮助,
UPDATE table1 as t1
SET
t1.field1 = (CASE
WHEN (select p.cnt from (SELECT COUNT(*) as cnt FROM table1 t2 WHERE t2.field1= 1) as p) < 100 THEN 1
WHEN (select p.cnt from (SELECT COUNT(*) as cnt FROM table1 t2 WHERE t2.field1= 2) as p) < 100 THEN 2
WHEN (select p.cnt from (SELECT COUNT(*) as cnt FROM table1 t2 WHERE t2.field1= 3) as p) < 100 THEN 3
WHEN (select p.cnt from (SELECT COUNT(*) as cnt FROM table1 t2 WHERE t2.field1= 4) as p) < 100 THEN 4
WHEN (select p.cnt from (SELECT COUNT(*) as cnt FROM table1 t2 WHERE t2.field1= 5) as p) < 100 THEN 5
END)
WHERE t1.id IN(100, 200, 300)
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