MySQL Learning summary----Single-table data query

MySQL Learning summary----Single-table data query

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First, the basic data record query

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1. Simple data query

• Select id,name,sex,class,address from qiuuuu; query all information in the table qiuuuu;

• Select Id,name,sex from Qiuuuu; The fields in the query table qiuuuu id,name,sex All information for three properties;

• Select * from qiuuuu; query all information for all fields in table qiuuuu;

2. Avoid duplicate data query distinct

• Select DISTINCT class from qiuuuu; query table qiuuuu all records about attribute class, no duplicates;

3, arithmetic character query

+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Seeking redundancy

• Select id*2 from qiuuuu

4. Display Format data query

mysql> Select concat (name, '------test: ', id) hello from qiuuuu;

Concat the connection string, enclosing the property name and string in parentheses, followed by the printed table name.

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

| Hello |

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

| James------Test:1 |

| Allen------Test:2 |

| Zhang------Test:3 |

| XI------Test:3 |

| XI------Test:3 |

| Li------Test:3 |

| Wang------Test:3 |

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

7 Rows in Set (0.00 sec)

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Second, the condition data record query

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In the MySQL database, the query is implemented through the SQL statement Select, while filtering the queried data records through the keyword where syntax is as follows:

Select Property Name 1, property name 2, property name 3,....., property name n from Qiuuuu where ...

You can answer the keyword in the following field:

• Between and

• Is null

• Inch

• Like
  

Comparison operators are:

>	Greater than
<	Less than
=	Equals
！ = or <>	Not equal to
>=	Greater than or equal
<=	Less than or equal

The logical operators are:

And OR &&	And
OR OR | |	Logical OR
Xor	XOR or
Not OR!	Non -

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Third, sort data record query

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Select Property Name 1, property name 2, property name 2,......, property name n from table name

where CONDITION order by property name M [Asc|desc] [, property name I [Asc|desc],]

1. Sort by single field

• Select ID from qiuuuu where class= ' 3 ' ORDER by id desc; Descending

• Select ID from qiuuuu where class= ' 3 ' ORDER by ID ASC; Ascending (the default ascending order)

2. Sort by multiple fields

SELECT * from qiuuuu where class= ' 3 ' ORDER by ID desc,address ASC;

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Iv. limit the number of data record queries

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V. Statistical functions and packet data record queries

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This article from "Doublelinux" blog, declined reprint!

MySQL Learning summary----Single-table data query