问题 1 -

SELECT * FROM table1 INNER JOIN table 2 ON table1.C_Eth_O = table2.Eth_ID

问题 2 -

SELECT * FROM table1 INNER JOIN table4 ON table1.C_ID = table4.C1_ID INNER JOIN table3 ON table3.Ail_ID = table4.Ail1_ID

问题 3 -

SELECT * FROM table1 INNER JOIN table5 ON table1.C_ID = table5.C1_ID INNER JOIN table6 ON table5.Cf1_ID = table6.Cf_ID INNER JOIN table3 ON table3.Ail_ID = table6.Ail1_ID