mysql addition, deletion, query and modification

The database is the core of modern information management, and the mysql database is even more popular. The operations of mysql are mainly divided into four basic operations: add, delete, check, and modify. This article will discuss the details of the operation of mysql, add, delete, check, and modify in detail.

1. Add data

Adding data is the first step in database operation and it is also the simplest operation. Mysql can use the INSERT statement to add data to the table in the database. The syntax is as follows:

INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);

Among them, table_name is the target table name, column1, column2, column3, etc. are column names, separated by commas, VALUES This is followed by the values ​​to be inserted, separated by commas. For example, if we want to insert a record into the student table, the record includes fields such as student number, name, age, gender, etc., we can use the following code:

INSERT INTO student (student_id, name, age, gender)
VALUES ('10001', '张三', 20, '男');

In this way, a record is added to the student table.

2. Deleting data

Deleting data is one of the common operations in the database. In mysql, you can use the DELETE statement to delete data in a table. The syntax of the DELETE statement is as follows:

DELETE FROM table_name WHERE condition;

Among them, table_name is the name of the table to be deleted, and the WHERE clause is optional and is used to filter rows that meet the conditions. For example, if we want to delete the record with the middle school ID 10001 in the student table, we can use the following code:

DELETE FROM student WHERE student_id = '10001';

In this way, the record with the middle school ID 10001 in the student table is deleted.

3. Querying data

Querying data is one of the most common operations in database applications. In mysql, you can use the SELECT statement to query the data in the table. The syntax of the SELECT statement is as follows:

SELECT column1, column2, ... FROM table_name WHERE condition;

Among them, column1, column2, etc. are the column names to be queried, separated by commas, and * can be used to replace all columns; table_name is the name of the table to be queried; WHERE sub clause is optional and is used to filter rows that meet the criteria. For example, if we want to query the student IDs and names of all students in the student table, we can use the following code:

SELECT student_id, name FROM student;

In this way, we can query the student IDs and names of all students in the student table.

4. Modify data

Modifying data is also one of the common operations in the database. In mysql, you can use the UPDATE statement to modify the data in the table. The syntax of the UPDATE statement is as follows:

UPDATE table_name SET column1=value1, column2=value2, ... WHERE condition;

Among them, table_name is the name of the table to be modified, and the SET clause is used to set the column and value to be modified. You can use commas to separate multiple assignment statements. On; the WHERE clause is optional and is used to filter rows that meet the criteria. For example, if we want to modify the age and gender of the record with the middle school number 10001 in the student table, we can use the following code:

UPDATE student SET age=21, gender='女' WHERE student_id='10001';

In this way, the age and gender of the record with the middle school number 10001 in the student table are modified.

Summary:

The four basic operations of adding, deleting, checking and modifying mysql are indispensable basic operations for developers. Proficient in these four operations can basically solve most database application development needs. In addition, things need to be paid attention to in actual operations, such as using transaction control to avoid data conflicts; using indexes to optimize query efficiency, etc. Before use, you must carefully understand the operation process of mysql and operate with caution to avoid irreparable losses caused by misoperation.

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