How to query numbers in mysql

With the increasing popularity of database applications, SQL language, as an important tool for operating databases, has become one of the basic skills necessary for programmers. For the problem of querying numbers in MySQL, generally speaking, you can use comparison operators (>,<,=,>=,<=) to query. In practical applications, some other query methods can also be used according to the query requirements and data characteristics, which will be introduced one by one below.

1. Use comparison operators

Comparison operators are the most basic query method. According to comparison operators, numbers are compared to filter out records that meet the conditions. . For example, to query all records in a table whose age field is greater than 18, you can use the following SQL statement:

SELECT * FROM table_name WHERE age > 18;

The query results will include all records that meet the conditions Record.

2. Use BETWEEN ... AND ...

If you need to query the records whose value of a certain field is within a certain range, you can use BETWEEN ... AND...statement. For example, to query all records in a table whose age field is between 18 and 30 years old, you can use the following SQL statement:

SELECT * FROM table_name WHERE age BETWEEN 18 AND 30;

Query results All records that meet the criteria will be included.

3. Use IN...

If you need to query records that a certain field matches a specific set of values, you can use the IN... statement. For example, to query all records in a table whose city fields are Beijing, Shanghai and Guangzhou, you can use the following SQL statement:

SELECT * FROM table_name WHERE city IN ('Beijing', 'Shanghai', 'Guangzhou') ;

The query results will include all records that meet the conditions.

4. Use LIKE...

If you need to query records that a certain field matches a certain pattern, you can use the LIKE... statement. For example, to query all records in a table whose name field starts with 'Zhang', you can use the following SQL statement:

SELECT * FROM table_name WHERE name LIKE 'Zhang%';

The query result will be Contains all records that meet the criteria.

5. Use COUNT...

If you need to query the number of occurrences of specific data in a field, you can use the COUNT... statement. For example, to query the number of records with the gender field 'male' in a table, you can use the following SQL statement:

SELECT COUNT(*) FROM table_name WHERE gender = 'male';

Query results The number of records matching the criteria will be returned.

To sum up, there are many ways to query numbers in MySQL. According to different query requirements, you can choose different query methods to achieve it. At the same time, in practical applications, SQL statements should be used flexibly to improve query efficiency and accuracy.

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