Summarize some common PHP table query statements

As a PHP programmer, I often come into contact with database operations. Among them, querying the data table is one of the most common operations. This article will introduce you to the table query statements in PHP.

1. Basic syntax of SELECT

In PHP, you need to use the SELECT statement to query the data table. The basic syntax is:

SELECT column_name(s) FROM table_name

Among them, column_name(s) represents the column name that needs to be queried, and "*" can be used to represent all columns; table_name is the required Query table name. In practical applications, if you need to query multiple tables, you need to use multi-table join query.

For example:

SELECT * FROM users

2. WHERE clause

Through the WHERE clause, we can set query conditions in the SELECT statement, So as to filter out the data we need. The syntax is:

SELECT column_name(s) FROM table_name WHERE condition

Among them, condition is the query condition we set. You can use various operators (=, , >, =,

For example:

SELECT * FROM users WHERE id=1

SELECT * FROM users WHERE username LIKE '%tom%'

3. ORDER BY Clause

Using the ORDER BY clause, we can sort the queried data according to the specified column. The syntax is:

SELECT column_name(s) FROM table_name ORDER BY column_name(s) ASC|DESC

Among them, ASC means sorting in ascending order, DESC means sorting in descending order, and the default is ascending order.

For example:

SELECT * FROM users ORDER BY age DESC

4. LIMIT clause

The LIMIT clause is used to limit the number of query results returned . The syntax is:

SELECT column_name(s) FROM table_name LIMIT start, end

where start represents the starting position and end represents the ending position. If there is only one parameter end, it means returning the previous end data.

For example:

SELECT * FROM users LIMIT 0, 10

SELECT * FROM users LIMIT 10

5. GROUP BY clause

Using the GROUP BY clause, we can perform group statistics on the queried data. The syntax is:

SELECT column_name(s) FROM table_name GROUP BY column_name(s)

For example:

SELECT sex, count(*) FROM users GROUP BY sex

The above are common PHP table query statements. If you master the above knowledge points, I believe your query operations will be more convenient and efficient.

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