Question

我打算写一个SQL请求UPDATE，我想验证table2.fld5是否已包含＆＃39; Hello＆＃39;为了不多次写，但没有找到实现此验证的方法。

请求是：

UPDATE table2
    SET fld5 = concat(fld5, 'Hello')
    WHERE NOT EXISTS (SELECT *
                      FROM table1
                      WHERE table1.fld1 = table2.fld1 AND
                            table1.fld2 = table2.fld2 AND
                            table1.fld3 = table2.fld3
                     )
     AND table2.fld4 > (NOW() - INTERVAL '79 MINUTE');

Answer 1

如何将条件添加到where：

UPDATE table2
    SET fld5 = concat(fld5, 'Hello')
    WHERE (fld5 not like '%Hello' OR fld5 IS NULL) AND  -- perhaps this should be '%Hello%'
          NOT EXISTS (SELECT *
                      FROM table1
                      WHERE table1.fld1 = table2.fld1 AND
                            table1.fld2 = table2.fld2 AND
                            table1.fld3 = table2.fld3 AND
                            table2.fld4 > (NOW() - INTERVAL '79 MINUTE')
                     );

我同意有关fld4比较的评论。我认为这是逻辑：

UPDATE table2
    SET fld5 = concat(fld5, 'Hello')
    WHERE (table2.fld5 not like '%Hello' OR table2.fld5 IS NULL) AND  -- perhaps this should be '%Hello%' AND
          table2.fld4 > (NOW() - INTERVAL '79 MINUTE') AND  -- or should this be <
          NOT EXISTS (SELECT *
                      FROM table1
                      WHERE table1.fld1 = table2.fld1 AND
                            table1.fld2 = table2.fld2 AND
                            table1.fld3 = table2.fld3                                
                     );

Answer 2

也许您的日期检查需要在exists子查询之外：

UPDATE table2 SET fld5 = concat(fld5, 'Hello') 
WHERE fld5 NOT LIKE '%Hello%' AND table2.fld4 > (NOW() - INTERVAL '79 MINUTE'
AND NOT EXISTS (SELECT * FROM table1 WHERE table1.fld1 = table2.fld1 AND table1.fld2 = table2.fld2 AND table1.fld3 = table2.fld3))

Postgresql在UPDATE请求中添加WHERE子句

2 个答案: