达梦数据库和常用数据库对比

达梦merge into 用法：根据指定条件判断原表的数据是否存在于目标表中，如果存在执行更新操作，如果不存在执行插入操作，从而实现数据的合并；

sql....
MERGE INTO目标表
USING 源表
ON (合并条件)
WHEN MATCHED THEN
UPDATE SET (更新操作)
WHEN NOT MATCHED THENINSERT(插入操作)

.....

merge into T_GZXJ_ZHYQ_ZHGW_GXJBQK_CDTJ t1
using (SELECT  TYPE ,sum(value) value FROM (
SELECT CASE WHEN LENGTH(replace(replace(TYPE,'大地',''),'洪滩',''))!=4 AND replace(replace(TYPE,'大地',''),'洪滩','')!='冷凝水' THEN concat(replace(replace(TYPE,'大地',''),'洪滩',''),'管线')
WHEN replace(replace(TYPE,'大地',''),'洪滩','')='冷凝水' THEN ' 冷凝水' ELSE replace(replace(TYPE,'大地',''),'洪滩','') END as
TYPE,value FROM t_gzxj_zhyq_zhgw_gxjbqk_xqtj WHERE tjl='管线管径'
) GROUP BY TYPE ORDER BY value DESC) t
on (t."TYPE" = t1."KEYNAME")
when matched then 
  update  set t1."value" = t."value";

oracle merge into用法:

MERGE INTO target_table USING source_table
ON condition
WHEN MATCHED THEN
  UPDATE SET Column1 = value1, column2 = value2
WHEN NOT MATCHED THEN
  INSERT (column1, column2) VALUES (value1, value2);

mysql 不能使用merge into语句：使用其他替换语句