Common Problem
Can the create statement be used to create a table structure and append new records?
Can the create statement be used to create a table structure and append new records?
cannot. The function of the CREATE statement is to create a table structure, but it cannot append new records. You can use the INSERT statement to append new records. The CREATE statement can be used to create a new table in the database and specify the attributes and constraints of the data columns; however, the newly created table is an empty table and requires the use of the INSERT statement to append new records. The INSERT statement is used to insert one or more rows of tuple data into an existing table in the database.
The operating environment of this tutorial: windows7 system, mysql8, Dell G3 computer.
"The create statement is used to create a table structure and append new records" is wrong.
The function of the CREATE statement is to create a table structure, but it cannot append new records. You can use the INSERT statement to append new records.
CREATE statement
The CREATE statement can be used to create a new table in the database; the process of creating a data table specifies the attributes of the data columns The process is also the process of enforcing data integrity (including entity integrity, referential integrity and domain integrity) constraints.
The syntax format for creating a table is:
CREATE TABLE <表名> ([表定义选项])[表选项][分区选项];
Among them, the format of [Table definition option] is:
<列名1> <类型1> [,…] <列名n> <类型n>
CREATE TABLE command syntax is more, among which It is mainly composed of table creation definition (create-definition), table options (table-options) and partition options (partition-options).
Here we first describe a simple example of creating a new table, and then focus on some main syntax knowledge points in the CREATE TABLE command.
The main syntax and usage instructions of the CREATE TABLE statement are as follows:
CREATE TABLE: used to create a table with a given name, you must have table CREATE permissions.
: Specifies the name of the table to be created, given after CREATE TABLE, and must comply with the identifier naming rules. The table name is specified as db_name.tbl_name to create the table in a specific database. It can be created this way regardless of whether there is a current database. db-name can be omitted when creating a table in the current database. If you use quoted distinguished names, the database and table names should be quoted separately. For example, 'mydb'.'mytbl' is legal, but 'mydb.mytbl' is not.
: Table creation definition, consisting of column name (col_name), column definition (column_definition), and possible null value specifications, integrity constraints, or table indexes composition.
By default, the table is created in the current database. If the table already exists, there is no current database, or the database does not exist, an error will occur.
Example: Create tb_courses data table
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) );
Copy after login
Check the data of tb_emp1 data table
SELECT * FROM tb_courses;
Copy after loginYou can see that the newly created table does not contain data. Inserting records requires the use of the INSERT statement.
INSERT statement
The INSERT statement can insert one or more rows of tuple data into an existing table in the database.
The INSERT statement has two syntax forms, namely the INSERT…VALUES statement and the INSERT…SET statement.
1) INSERT…VALUES statement
INSERT VALUES 的语法格式为： INSERT INTO <表名> [ <列名1> [ , … <列名n>] ] VALUES (值1) [… , (值n) ];
Copy after loginThe syntax is explained as follows.
: Specify the name of the table to be operated on.
: Specify the column name into which data needs to be inserted. If data is inserted into all columns in the table, all column names can be omitted, and INSERT VALUES(…) can be used directly.
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>, …Copy after loginThis statement is used to directly add data to the table. Certain columns specify corresponding column values, 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. The default value for this column.
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.
Example: Add values to all fields in the table
Insert a new record in the tb_courses table, course_id value is 1, course_name value is "Network", course_grade The value is 3 and the info value is "Computer Network".
INSERT INTO tb_courses (course_id,course_name,course_grade,course_info) VALUES(1,'Network',3,'Computer Network');
Copy after login#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.
【Related recommendations: mysql video tutorial】
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