如何基于SQL Server中的主表列值加入表？

Question

我有以下3个表格：

MAIN_TABLE：

id,name,table_type
1a,sas,1
2a,saw,1
3a,sdd,2

inst_table

id,inst_name,rating
1a,sdsdf,3
2a,erer,4

indv_table

id,ind_name,rating
3a,gbgbg,3
5a,gff,4

如何根据main_table column:'table_type'加入子表？

即如果main table column: table_type = 1，则必须加入table:'inst_table'其他table:'indv_table'

Answer 1

SELECT *
  FROM main_table t1
    INNER JOIN inst_table t2 ON T1.ID = T2.ID where t1.table_type=1
UNION ALL
  SELECT *
  FROM main_table T1
    INNER JOIN indv_table T3 ON T1.ID = T3.ID where t1.table_type=2

Answer 2

您可以将两个子表连接到main_table：

proc sql;
select m.*, i.*, d.* 
from main_table as m 
left join inst_table as i on m.id=i.id and m.table_type = 1
left join indv_table as d on m.id=d.id and m.table_type ne 1
;
quit;