MySQL multi-Table operations and Batch Processing

Multi-Table operations

Multiple tables may exist in a database, which are associated with each other. We will continue to use the previous example. The preceding table contains basic information about an employee, such as name, gender, date of birth, and place of birth. Create another table to describe the articles published by employees, including the author's name, article title, and publication date.

1. view the content of mytable in the first table:

Mysql> select * from mytable;

+ ---------- + ------ + ------------ + ----------- +

| Name | sex | birth | birthaddr |

+ ---------- + ------ + ------------ + ----------- +

| Abccs | f | 1977-07-07 | china |

| Mary | f | 1978-12-12 | usa |

| Tom | m | 1970-09-02 | usa |

+ ---------- + ------ + ------------ + ----------- +

2. Create the second table title (including the author, article title, and publication date ):

Mysql> create table title (writer varchar (20) not null,

-> Title varchar (40) not null,

-> Senddate date );

Add a record to the table. The contents of the last table are as follows:

Mysql>

Select * from title;

+ -------- + ------- + ------------ +

| Writer | title | senddate |

+ -------- + ------- + ------------ +

| Abccs | a1 | 2000-01-23 |

| Mary | b1 | 1998-03-21 |

| Abccs | a2 | 2000-12-04 |

| Tom | c1 | 1992-05-16 |

| Tom | c2 | maid |

+ -------- + ------- + ------------ +

5 rows in set (0.00sec)

3. Multi-Table query

Now we have two tables: mytable and title. Using these two tables, we can perform a Combined Query: for example, we want to query the name, gender, and Article of the author abccs:

Mysql> SELECT name, sex, title FROM mytable, title

-> WHERE name = writer AND name = 'abccs ′;

+ ------- + ------ + ------- +

| Name | sex | title |

+ ------- + ------ + ------- +

| Abccs | f | a1 |

| Abccs | f | a2 |

+ ------- + ------ + ------- +

In the above example, because the author's name, gender, and Article record are in two different tables, you must use a combination for query. You must specify how records in a table match those in other tables.

Note: If the writer column in the title of the second table is named name (the same as the name column in mytable) rather than writer, you must use mytable. name and title. name indicates the difference.

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