在几个sqlite表中进行连接是行不通的

Question

所以我有这个SQLite字符串

SELECT
a.anchor as [From Anchor],
c.anchor as [To Anchor]
FROM table1 a
JOIN table2 b ON b.toAnchor = a.anchor
JOIN table3 c ON c.anchor = b.fromAnchor

执行它时没有错误，但它返回一个空表。所有3个表中都有数据，数据确实符合预期，但我什么都没得到。

表1

filename | farea | anchor
_________________________
file.doc   N/A     srs100

表2

type | filename | fromAnchor | toAnchor
_______________________________________
SRS      N/A       srs100      crs888

表3

filename | farea | anchor
_________________________
file.doc   N/A     crs888

我知道我可以使用表2，但我需要这样做才能找到来自和不匹配的区域。

如果我找不到这样做的方法那么我想找到一种方法，我可以组合2个表，所以它会这样。

表1

type | filename | fromAnchor | toAnchor
_______________________________________
SRS      N/A       crs100      srs888

表2

type | filename | fromAnchor | toAnchor
_______________________________________
CRS      N/A       srs888      srd999

结果

crs    | srs    | srd
_______________________________________
crs888  srs888   srd999

如果需要，我可以提供更多信息。现在我想知道sql调用是否正确。

Answer 1

SELECT
a.anchor as [From Anchor],
c.anchor as [To Anchor]
FROM table1 a
JOIN table2 b ON b.fromAnchor = a.anchor
JOIN table3 c ON c.anchor = b.toAnchor

Answer 2

试试这个

SELECT 
fromAnchor, 
toAnchor 
from table2 a
join table1 b on  a.fromAnchor =b.anchor
join table3 c on a.toAnchor =c.anchor

Answer 3

原来数据库中的数据配置不正确。结果证明是有效的。

SELECT
TABLE1.toAnchor AS CRS,
TABLE1.fromAnchor AS SRS
FROM tbl_traces_srstraces
LEFT JOIN TABLE2 ON TABLE2.anchor = TABLE1.toAnchor
LEFT JOIN TABLE3 ON TABLE3.anchor = TABLE1.fromAnchor