本文介绍一下Oracle merge合并函数，业务场景：新增数据的时候要先查询数据库是否已经有改数据，有数据就更新数据，没数据才新增数据，这是很常见的业务场景，如果是用Oracle数据库的话，其实直接用merge函数效率更快，而且merge函数性能也相对比较好
merge函数的语法：
MERGE INTO table_name alias1
USING (table|view|sub_query) alias2
ON (join condition)
WHEN MATCHED THEN
UPDATE table_name
SET col1 = col_val1,
col2 = col_val2
WHEN NOT MATCHED THEN
INSERT (column_list) VALUES (column_values);
举个例子：
SQL实现，意思是有数据就更新，没数据才新增
MERGE INTO t_config_related A1 USING(select '97547758-6f85-419e-85f9-b8f711ca2660' seq,
'97547758-6f85-419e-85f9-b8f711ca2658' tipsSeq,
to_number('1') appLevel,
'24e1ccc38d9542189d1cc6c23f814a18' relaSeq from dual) A2
ON(A1.seq = A2.seq)
WHEN MATCHED THEN
UPDATE SET
A1.tips_seq = A2.tipsSeq,
A1.app_level = A2.appLevel,
A1.rela_seq = A2.relaSeq
WHEN NOT MATCHED THEN
INSERT(seq , tips_seq , app_level , rela_seq)
VALUES(A2.seq , A2.tipsSeq , A2.appLevel , A2.relaSeq);
/**
* 批量更新保存地区关联信息
* @date 2019年2月21日上午11:17:10
* @return
*/
@RequestMapping("/batchSaveTipsAreaConfig")
@ResponseBody
public ResultModel batchSaveTipsConfig(ApprTipsRelatedModel relatedModel) {
List<ApprTipsRelatedModel> areaTipsList = new ArrayList<ApprTipsRelatedModel>();
//封装批量更新的地区列表
String[] areaSeqs = StringUtils.split(relatedModel.getAreaSeq(),",");
for (String areaSeq : areaSeqs) {
ApprTipsRelatedModel areaRelatedModelNew = new ApprTipsRelatedModel();
areaRelatedModelNew.setSeq(commonService.generateUUID());
areaRelatedModelNew.setTipsSeq(relatedModel.getTipsSeq());
areaRelatedModelNew.setAppLevel(NumConstant.COMMON_NUM_TREE);
areaRelatedModelNew.setRelaSeq(areaSeq);
areaTipsList.add(areaRelatedModelNew);
}
//批量更新新增数据
try {
this.tipsConfigService.batchSaveTipsRelatedConfig(areaTipsList);
return ResultModel.success("保存成功");
} catch(Exception e) {
logger.error("批量绑定地区异常:{}"+e);
throw new SuperControllerException();
}
}
注意要点：
在开发中我遇到一个异常，mybatis打印出来的SQL是这样的：
Preparing: MERGE INTO appr_tips_config_related A1 ? USING( ? ? ? ? ? select ? seq , ? tipsSeq , ? appLevel , ? relaSeq from dual ? ? ? ? ) A2 ? ON( ? ? ? ? ?A1.seq = A2.seq ? ? ?) ? WHEN MATCHED THEN ? ? UPDATE SET A1.seq = A2.seq, A1.tips_seq = A2.tipsSeq, A1.app_level = A2.appLevel, A1.rela_seq = A2.relaSeq ? ? ?WHEN NOT MATCHED THEN ? ? ?INSERT(seq,tip_seq,app_level,rela_seq) ? ? ? ? VALUES(A2.seq , A2.tipsSeq , A2.appLevel , A2.relaSeq)
可以看出什么问题？打印出的SQL有很多问号，那是因为SQL有空格导致的，所以使用merge函数不用随便加空格，不然会报错的
? USING( ? ? ? ? ? select ? seq , ? tipsSeq , ? appLevel , ? relaSeq from dual ? ? ? ? ) A2 ? ON( ? ? ? ? ?A1.seq = A2.seq ? ? ?) ?