MYSQL Correlation Query

1. Internal connection

Connect the same meaning field in two tables and return the information that is present in the two tables:

SELECT * from Tablea,tableb where TableA. field c=tableb. field C;

SELECT * FROM TableA inner join TableB on TableA. field c=tableb. field C;

TableA. field C=tableb. field C is a filter condition.

2. Left Outer connection

Use each record in the first table to match the record for the second table, regardless of whether it matches the record, the query results show all the contents of the first table

SELECT * from TableA left outer joins TableB on TableA. field c=tableb. field C;

3. Right outer connection

Use each record in the second table to match the record for the first table, regardless of whether it matches the record, the query results show all the contents of the second table

SELECT * FROM TableA right outer join TableB on TableA. field c=tableb. field C;

4. Full connection

Left OUTER join and right outer JOIN and set

SELECT * from TableA left outer joins TableB on TableA. field C=tableb. field C Union select * FROM TableA right outer join TableB on TableA. field C=tableb. field C

5. Correlated sub-query

The result of the first query is used as a condition for the second query.

MYSQL Correlation Query