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1.3 Multi-table query

1.3.1 join query:

# Internal connection:

Self-join query:

# external connection

Left outer join (all records of table name 1 can be queried, but only matching records can be found in table name 2)

SELECT attribute name list FROM table name 1 LEFT JOIN table name 2 ON table name 1. Attribute name 1 = table name 2. Attribute name 2

# right outer connection (all records of table name 2 can be queried, but only matching records can be found in table name 1):

Insert some values into the right table first:

Then do the right outer join query:

1.4 modify the fields of some records

Earlier, I briefly introduced insert into and select * from, and then I went on to say change.

1.4.1 single table update

The simplest expression is:

Add some more restrictions as follows:

The results are as follows:

1.4.2 Multi-table update

Well, this example is of no use at all, because we are only associated with sid, which can be written separately as two updates.

However, in the case of multiple table updates, if there are two related tables, such as the roll-out table and the transfer-in table, there are interdependent keys, so that some states are closely related and updated together. (it seems to be OK with transactions.)

……

The above results are as follows:

1.5 Delete

For a detailed mysql deletion operation, you can view the article

Http://www.cnblogs.com/ggjucheng/archive/2012/11/06/2756420.html

Single table record deletion:

DELETE FROM table name WHERE conditional expression [ORDER BY field] [number of LIMIT record rows]

The original data went like this:

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