SqlServer 中ISNULL(a.DEALTIME,'')=''

这段代码的含义是：如果a.DEALTIME的值为NULL或空字符串，则返回TRUE，否则返回FALSE。在这个表达式中，使用了ISNULL函数来判断a.DEALTIME是否为NULL，如果是NULL，则返回空字符串''，然后再和空字符串''进行比较。如果a.DEALTIME不是NULL，那么就直接和空字符串''进行比较。这个表达式通常用来判断某个字段是否为空，以便在查询中进行筛选或者计算。

相关问题

UPDATE a SET a.refund_status = b.dealstat , a.refund_time = b.dealtime FROM dwi_store_setmt_ord_dtl_p a INNER JOIN sdi_dgmps_dgmpsdb_mstore.chainstorefeemangdtl_p b ON a.comp_code = trim(upper(b.companycode)) AND a.src_pid = trim(b.pid) WHERE a.refund_status = 0 AND ISNULL(a.refund_time,'') = '' AND b.dealstat = 1 AND ISNULL(a.dealtime,'') <> '' ;改为用merge into 更新

Sure, here's the equivalent MERGE statement:

MERGE INTO dwi_store_setmt_ord_dtl_p AS a
USING (
    SELECT trim(upper(b.companycode)) AS comp_code,
           trim(b.pid) AS src_pid,
           b.dealstat,
           b.dealtime
    FROM sdi_dgmps_dgmpsdb_mstore.chainstorefeemangdtl_p AS b
    WHERE b.dealstat = 1
) AS b
ON a.comp_code = b.comp_code
   AND a.src_pid = b.src_pid
   AND a.refund_status = 0
   AND ISNULL(a.refund_time, '') = ''
   AND ISNULL(a.dealtime, '') <> ''
WHEN MATCHED THEN
    UPDATE SET a.refund_status = b.dealstat,
               a.refund_time = b.dealtime;

This MERGE statement combines the source table `sdi_dgmps_dgmpsdb_mstore.chainstorefeemangdtl_p` with the target table `dwi_store_setmt_ord_dtl_p` based on the matching conditions specified in the ON clause. When a match is found, the specified columns in the target table are updated with the corresponding values from the source table.

表A字段:UUID,ITEMNO,dealtime,flag,gid;用 UUID,ITEMNO分组取分组后条数大于1的数据,数据存入表B,biaoB组内再根据dealtime从大到小排序,保留dealtime最大的一条数据,dealtime一样时也只保留一条

可以使用以下 SQL 语句实现：

INSERT INTO biaoB (UUID, ITEMNO, dealtime, flag, gid)
SELECT UUID, ITEMNO, MAX(dealtime), flag, gid
FROM biaoA
GROUP BY UUID, ITEMNO
HAVING COUNT(*) > 1;

这条 SQL 语句会将表 A 中按 UUID 和 ITEMNO 分组后，分组内数据条数大于 1 的数据插入到表 B 中。在插入时，会根据 dealtime 从大到小排序，并只保留 dealtime 最大的一条数据（如果有多条 dealtime 相同的记录，则只保留其中的一条）。