我的left join失效了，用了left join后跟没用一样

[钛元素]

SELECT A.LCBH AS [流程编号], A.SQRQ AS [申请日期], C.lastname AS [申请人], D.departmentname AS [所属部门], A.ccsy AS [报销事由], 
E.subcompanyname AS [付款单位], A.ccksrq AS [出差开始日期], A.ccjsrq AS [出差结束日期], 
F.name AS [预算科目], G.name AS [研发其他选项], 
CASE B.cdztlx WHEN 0 THEN '个人' WHEN 1 THEN '部门'  WHEN 2 THEN '分部'  WHEN 3 THEN '成本中心'  END  AS [承担主体类型],
H.departmentname AS [承担主体], B.fyrq AS [费用日期], B.qqdd AS [起讫地点], B.ts AS [天数], B.fjp AS [飞机票], 
B.qcp AS [汽车票], B.hcp AS [火车票], B.zsf AS [住宿费], B.zdf AS [招待费], B.hsbt AS [伙食补贴],
B.jtbt AS [交通补贴], B.qt AS [其他], B.bxjexj AS [报销金额小计], B.zy AS [摘要], B.sbje AS [实报金额]
FROM formtable_main_101 A
LEFT JOIN formtable_main_101_dt1 B ON A.id = B.mainid
LEFT JOIN HrmResource C ON A.sqr = C.id
LEFT JOIN HrmDepartment D ON A.ssbm = D.id 
LEFT JOIN hrmsubcompany E ON A.fkdw = E.id
LEFT JOIN fnabudgetfeetype F ON B.yskm = F.id
LEFT JOIN mode_selectitempagedetail G ON B.yfqtxx = G.disorder
LEFT JOIN HrmDepartment H ON B.cdzt = H.id

WHERE F.archive <> 1 AND G.mianid = 89

就是红色部分，去掉就显示700多条，加上就只有55条，跟join一样，left失效了。help！

 

 

[钛元素]

搜到了，谢谢 https://blog.csdn.net/foosir/article/details/122517387?spm=1035.2023.3001.6557&utm_medium=distribute.pc_relevant_bbs_down_v2.none-task-blog-2~default~OPENSEARCH~Rate-4-122517387-bbs-619418115.264^v3^pc_relevant_bbs_down_v2_opensearchbbsnew&depth_1-utm_source=distribute.pc_relevant_bbs_down_v2.none-task-blog-2~default~OPENSEARCH~Rate-4-122517387-bbs-619418115.264^v3^pc_relevant_bbs_down_v2_opensearchbbsnew

[二月十六]

left join 后on的条件不会减少数据，可能数据会变多，比如
id
1

id
1
2
1

这样关联会出来两条数据，但是如果在where条件里写了t2 的字段条件，就可能会出现数据变少的情况，比如t2.id=2 这样的话，一条数据也出不来了