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This article mainly introduces mysql how to query all the fields of data, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let Xiaobian take you to understand.

In mysql, you can use the select statement to query the data for all fields, using the syntax "SELECT * FROM table name;" or "SELECT all field names list FROM table name;".

The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.

In MySQL, you can use SELECT statements to query data. Query data refers to the use of different query methods to obtain different data from the database according to the requirements, which is the most frequent and important operation.

How does mysql query the data of all fields?

Querying all fields refers to the data of all fields in the query table. MySQL provides the following two ways to query all fields in a table.

Query all fields using the "*" wildcard

List all fields of the table

1) use "*" to query all fields of the table

SELECT can use "*" to find data for all fields in the table. The syntax format is as follows:

SELECT * FROM table name

When using a "*" query, you can only arrange the fields in the order of the data table, not change the order of the fields.

Example 1

Query the data for all fields from the tb_students_info table, and the SQL statement and run results are shown below.

Mysql > use test_db;Database changedmysql > SELECT * FROM tb_students_info +-+ | id | name | dept_id | age | sex | height | login_date | + -+-+ | 1 | Dany | 1 | 25 | F | 2015 | 09-10 | 2 | Green | 3 | 23 | F | 2016-10-22 | 3 | Henry | 2 | 23 | M | 2015-05-31 | 4 | Jane | 1 | 22 | F | 2016-12-20 | 5 | | Jim | 1 | 24 | M | 2016 | 01-15 | | 6 | John | 2 | 21 | M | 2015 | 11-11 | | 7 | Lily | 6 | 22 | F | 2016-02-26 | 8 | Susan | 4 | 23 | F | 2015-10-01 | 9 | Thomas | 3 | 22 | M | 2016-06-07 | | | 10 | Tom | 4 | 23 | M | 165,165 | 2016-08-05 | +-+ 10 rows in set (0.26sec) |

The result shows that when you use the "*" wildcard, all columns are returned, and the data columns are displayed in the order in which the table was created.

Note: in general, it is best not to use the wildcard "*" unless you need to use all the field data in the table. Although using wildcards can save time entering query statements, getting unwanted column data usually reduces the efficiency of the query and the application used. The advantage of using "*" is that when you don't know the names of the columns you want, you can get them through "*".

2) list all fields of the table

The field after the SELECT keyword is called the field you want to find, so you can follow the names of all fields in the table after the SELECT keyword. If you forget the field name, you can use the DESC command to view the structure of the table.

The syntax format is as follows:

SELECT all Field names list FROM Table name

Sometimes, because there are so many fields in the table, you may not be able to remember the names of all the fields, so this method is inconvenient and is not recommended.

Example 2

To query all the data in the tb_students_info table, the SQL statement can also be written as follows:

SELECT id,name,dept_id,age,sex,height,login_date FROM tb_students_info

The running result is the same as in example 1.

This query method is more flexible. If you need to change the order in which the fields are displayed, you only need to adjust the order of the list of fields after the SELECT keyword.

Although it is flexible to list all the fields of a table, the "*" wildcard is usually used when querying all fields. Using the "*" approach is relatively simple, especially when there are a lot of fields in the table, the advantage of this approach is more obvious. Of course, if you need to change the order in which the fields are displayed, you can choose to list all the fields in the table.

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