Mysql method of inserting multiple pieces of data: 1. Use the "INSERT INTO table name field list VALUES (value 1) ..., (value n);" statement to insert data; 2. Use "INSERT INTO table name SET Field 1 = value 1, field 2 = value 2,..." statement inserts data.
#After the database and table are successfully created, data needs to be inserted into the database table. In MySQL, you can use the INSERT statement to insert one or more rows of tuple data into an existing table in the database.
Basic syntax
The INSERT statement has two syntax forms, namely the INSERT…VALUES statement and the INSERT…SET statement.
1) INSERT...VALUES statement
The syntax format of INSERT VALUES is:
INSERT INTO <表名> [ <列名1> [ , … <列名n>] ] VALUES (值1) [… , (值n) ];
The syntax is explained as follows.
VALUES or VALUE clause: This clause contains the list of data to be inserted. The order of data in the data list should correspond to the order of columns.
2) INSERT...SET statement
The syntax format is:
INSERT INTO <表名> SET <列名1> = <值1>, <列名2> = <值2>, …
This statement is used to directly specify the corresponding values for certain columns in the table. The column value, that is, the column name of the data to be inserted is specified in the SET clause. col_name is the specified column name, and the equal sign is followed by the specified data. For unspecified columns, the column value will be specified as the default value of the column. .
It can be seen from the two forms of INSERT statement:
Use INSERT...VALUES statement to insert one row of data or multiple rows of data into the table;
Use the INSERT…SET statement to specify the value of each column in the inserted row, or to specify the values of some columns;
INSERT…SELECT statement Insert data from other tables into the table.
The INSERT…SET statement can be used to insert the values of some columns into the table, which is more flexible;
INSERT…VALUES statement Multiple pieces of data can be inserted at one time.
In MySQL, processing multiple inserts with a single INSERT statement is faster than using multiple INSERT statements.
When using a single INSERT statement to insert multiple rows of data, you only need to enclose each row of data in parentheses.
Add values to all fields in the table
Create a course information table tb_courses in the test_db database, including course number course_id, course name course_name, course credits course_grade and Course notes course_info, the input SQL statement and execution results are as follows.
mysql> CREATE TABLE tb_courses -> ( -> course_id INT NOT NULL AUTO_INCREMENT, -> course_name CHAR(40) NOT NULL, -> course_grade FLOAT NOT NULL, -> course_info CHAR(100) NULL, -> PRIMARY KEY(course_id) -> ); Query OK, 0 rows affected (0.00 sec)
There are two ways to insert values into all fields in the table: one is to specify all field names; the other is to not specify field names at all.
[Example 1] Insert a new record in the tb_courses table, the course_id value is 1, the course_name value is "Network", the course_grade value is 3, and the info value is "Computer Network".
Before performing the insert operation, view the SQL statement and execution results of the tb_courses table as follows.
mysql> SELECT * FROM tb_courses; Empty set (0.00 sec)
The query result shows that the current table content is empty and there is no data. Next, perform the operation of inserting data. The input SQL statement and execution process are as follows.
mysql> INSERT INTO tb_courses -> (course_id,course_name,course_grade,course_info) -> VALUES(1,'Network',3,'Computer Network'); Query OK, 1 rows affected (0.08 sec) mysql> SELECT * FROM tb_courses; +-----------+-------------+--------------+------------------+ | course_id | course_name | course_grade | course_info | +-----------+-------------+--------------+------------------+ | 1 | Network | 3 | Computer Network | +-----------+-------------+--------------+------------------+ 1 row in set (0.00 sec)
You can see that the record was inserted successfully. When inserting data, all fields of the tb_courses table are specified, so new values will be inserted for each field.
The order of the column names after the INSERT statement does not need to be the order when the tb_courses table is defined. That is, when inserting data, it is not necessary to insert in the order defined by the table, as long as the order of the values is the same as the order of the column fields.
[Example 2] Insert a new record in the tb_courses table, the course_id value is 2, the course_name value is "Database", the course_grade value is 3, and the info value is "MySQL". The input SQL statement and execution results are shown below.
mysql> INSERT INTO tb_courses -> (course_name,course_info,course_id,course_grade) -> VALUES('Database','MySQL',2,3); Query OK, 1 rows affected (0.08 sec) mysql> SELECT * FROM tb_courses; +-----------+-------------+--------------+------------------+ | course_id | course_name | course_grade | course_info | +-----------+-------------+--------------+------------------+ | 1 | Network | 3 | Computer Network | | 2 | Database | 3 | MySQL | +-----------+-------------+--------------+------------------+ 2 rows in set (0.00 sec)
When using INSERT to insert data, the column name list column_list is allowed to be empty. At this time, the value list needs to specify a value for each field of the table, and the order of the values must be the same as the order in which the fields are defined in the data table. same.
[Example 3] Insert a new record in the tb_courses table, the course_id value is 3, the course_name value is "Java", the course_grade value is 4, and the info value is "Jave EE". The input SQL statement and execution results are shown below.
mysql> INSERT INTO tb_courses -> VLAUES(3,'Java',4,'Java EE'); Query OK, 1 rows affected (0.08 sec) mysql> SELECT * FROM tb_courses; +-----------+-------------+--------------+------------------+ | course_id | course_name | course_grade | course_info | +-----------+-------------+--------------+------------------+ | 1 | Network | 3 | Computer Network | | 2 | Database | 3 | MySQL | | 3 | Java | 4 | Java EE | +-----------+-------------+--------------+------------------+ 3 rows in set (0.00 sec)
The INSERT statement does not specify an insertion list, only a value list. In this case, the value list specifies the inserted values for each field column, and the values must be in the same order as the fields are defined in the tb_courses table.
注意：虽然使用 INSERT 插入数据时可以忽略插入数据的列名称，若值不包含列名称，则 VALUES 关键字后面的值不仅要求完整，而且顺序必须和表定义时列的顺序相同。如果表的结构被修改，对列进行增加、删除或者位置改变操作，这些操作将使得用这种方式插入数据时的顺序也同时改变。如果指定列名称，就不会受到表结构改变的影响。
向表中指定字段添加值
为表的指定字段插入数据，是在 INSERT 语句中只向部分字段中插入值，而其他字段的值为表定义时的默认值。
【实例 4】在 tb_courses 表中插入一条新记录，course_name 值为“System”，course_grade 值为 3，course_info 值为“Operating System”，输入的 SQL 语句和执行结果如下所示。
mysql> INSERT INTO tb_courses -> (course_name,course_grade,course_info) -> VALUES('System',3,'Operation System'); Query OK, 1 rows affected (0.08 sec) mysql> SELECT * FROM tb_courses; +-----------+-------------+--------------+------------------+ | course_id | course_name | course_grade | course_info | +-----------+-------------+--------------+------------------+ | 1 | Network | 3 | Computer Network | | 2 | Database | 3 | MySQL | | 3 | Java | 4 | Java EE | | 4 | System | 3 | Operating System | +-----------+-------------+--------------+------------------+ 4 rows in set (0.00 sec)
可以看到插入记录成功。如查询结果显示，这里的 course_id 字段自动添加了一个整数值 4。这时的 course_id 字段为表的主键，不能为空，系统自动为该字段插入自增的序列值。在插入记录时，如果某些字段没有指定插入值，MySQL 将插入该字段定义时的默认值。
使用 INSERT INTO…FROM 语句复制表数据
INSERT INTO…SELECT…FROM 语句用于快速地从一个或多个表中取出数据，并将这些数据作为行数据插入另一个表中。
SELECT 子句返回的是一个查询到的结果集，INSERT 语句将这个结果集插入指定表中，结果集中的每行数据的字段数、字段的数据类型都必须与被操作的表完全一致。
在数据库 test_db 中创建一个与 tb_courses 表结构相同的数据表 tb_courses_new，创建表的 SQL 语句和执行过程如下所示。
mysql> CREATE TABLE tb_courses_new -> ( -> course_id INT NOT NULL AUTO_INCREMENT, -> course_name CHAR(40) NOT NULL, -> course_grade FLOAT NOT NULL, -> course_info CHAR(100) NULL, -> PRIMARY KEY(course_id) -> ); Query OK, 0 rows affected (0.00 sec) mysql> SELECT * FROM tb_courses_new; Empty set (0.00 sec)
【实例 5】从 tb_courses 表中查询所有的记录，并将其插入 tb_courses_new 表中。输入的 SQL 语句和执行结果如下所示。
mysql> INSERT INTO tb_courses_new -> (course_id,course_name,course_grade,course_info) -> SELECT course_id,course_name,course_grade,course_info -> FROM tb_courses; Query OK, 4 rows affected (0.17 sec) Records: 4 Duplicates: 0 Warnings: 0 mysql> SELECT * FROM tb_courses_new; +-----------+-------------+--------------+------------------+ | course_id | course_name | course_grade | course_info | +-----------+-------------+--------------+------------------+ | 1 | Network | 3 | Computer Network | | 2 | Database | 3 | MySQL | | 3 | Java | 4 | Java EE | | 4 | System | 3 | Operating System | +-----------+-------------+--------------+------------------+ 4 rows in set (0.00 sec)
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