左边将1个表连接到MYSQL中的多个表

I have 4 tables, which are linked together with a foreign key from another, eg Table 2 has fk_table1, Table 3 has fk_table2, Table 4 has fk_table3.

The first 3 tables in this chain all have corresponding data for each entry. However, Table 4 contain optional data, therefore, there may not be a corresponding entry for a field in say Table 3.

But I want those data from Table 4 too. This is currently what I have, but doesn't work.

SELECT *
        FROM T1, T2, T3 LEFT JOIN T4
        WHERE T1.t1 = T2.t1
        AND T2.t2 = T3.t2
        AND T3.t3 = T4.t3

If only T4 is optional, use LEFT JOIN only on that table:

SELECT *
FROM T1
JOIN T2 ON T1.t1 = T2.t1
JOIN T3 ON T2.t2 = T3.t2
LEFT JOIN T4 ON T3.t3 = T4.t3

Try this:

SELECT *
FROM T1
    LEFT JOIN T2 on T1.t1 = T2.t1
    LEFT JOIN T3 on T2.t2 = T3.t2
    LEFT JOIN T4 on T3.t3 = T4.t3

Update

Or if you want to only include rows where there is an appropriate row in T1, T2 or T3 you need to use an inner join.

SELECT *
FROM T1
    INNER JOIN T2 on T1.t1 = T2.t1
    INNER JOIN T3 on T2.t2 = T3.t2
    LEFT JOIN T4 on T3.t3 = T4.t3

To separate the logic of table joins it's possible to use brackets:

select 
    *
from 
    t1
    inner join t2 on t1.some_id = t2.some_id
    inner join (
        t3 
        left join t4 on t3.some_id = t4.some_id
    ) on t2.some_id = t3.some_id