Can the MySQL create statement be used to create a table structure and append new records

mysql create Statement can be used to create a table structure and append new records

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You can't .CREATE The function of the statement is to create a table structure , But new records cannot be added , Adding a new record can use INSERT sentence .CREATE Statement can be used to create a new table in the database , And specify the attributes and constraints of the data column ; But the new table is an empty table , Need to use INSERT Statement to append a new record .INSERT Statement is used to insert one or more rows of tuple data into the existing table in the database .

The operating environment of this tutorial ：windows7 System 、mysql8、Dell G3 The computer .

“create Statement is used to create a table structure and append new records ”, It's wrong. .

CREATE The function of the statement is to create a table structure , But new records cannot be added , Adding a new record can use INSERT sentence .

CREATE sentence

CREATE Statement can be used to create a new table in the database ; The process of creating a data table is to specify the attributes of data columns , At the same time, it is also the implementation of data integrity （ Including physical integrity 、 Referential integrity and domain integrity ） The process of constraint .

The syntax format of creating a table is ：

CREATE TABLE < Table name > ([ Table definition options ])[ Table options ][ Partition options ];

among ,[ Table definition options ] The format is ：

< Name 1> < type 1> [,…] < Name n> < type n>

CREATE TABLE More command syntax , It is mainly created and defined by the table （create-definition）、 Table options （table-options） And partition options （partition-options） Made up of .

Here is a simple example of creating a new table , And then focus on CREATE TABLE Some main syntax knowledge points in the command .

CREATE TABLE The main syntax and instructions of the sentence are as follows ：

• CREATE TABLE： Used to create a table with a given name , Must have table CREATE Authority .

• < Table name >： Specify the name of the table to be created , stay CREATE TABLE Then give , Must comply with identifier naming rules . The table name is specified as db_name.tbl_name, To create tables in a specific database . Whether or not there is a current database , Can be created in this way . When creating a table in the current database , It can be omitted db-name. If you use a quoted distinguished name , The database and table names should be quoted separately . for example ,'mydb'.'mytbl' It's legal. , but 'mydb.mytbl' illegal .

• < Table definition options >： Table creation definition , By column name （col_name）、 Definition of columns （column_definition） And possible null values 、 Integrity constraints or table indexes consist of .

• The default is , The table is created into the current database . If the table already exists 、 There is no current database or the database does not exist , There will be errors .

Example ： establish tb_courses Data sheet

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));

Check it out. tb_emp1 Data from data sheets

SELECT * FROM tb_courses;

You can see that the new table does not contain data . To insert a record, you need to use INSERT sentence .

INSERT sentence

INSERT Statement can insert one or more rows of tuple data into the existing tables in the database .

INSERT There are two grammatical forms of sentences , Namely INSERT…VALUES Statement and INSERT…SET sentence .

1) INSERT…VALUES sentence

INSERT VALUES  The grammar format of is ：INSERT INTO < Table name > [ < Name 1> [ , … < Name n>] ]VALUES ( value 1) [… , ( value n) ];

The grammar is as follows .

• < Table name >： Specifies the name of the table being manipulated .

• < Name >： Specify the name of the column to insert the data . If you insert data into all the columns in the table , Then all column names can be omitted , Direct adoption INSERT< Table name >VALUES(…) that will do .

• VALUES or VALUE Clause ： This clause contains the list of data to insert . The order of the data in the data list corresponds to the order of the columns .

2) INSERT…SET sentence

The grammar format is ：

INSERT INTO < Table name >SET < Name 1> = < value 1>,        < Name 2> = < value 2>,        …

This statement is used to specify the corresponding column values directly to some columns in the table , The column name of the data to be inserted is in SET Clause ,col_name For the specified column name , After the equal sign is the specified data , And for unspecified Columns , The column value is specified as the default value for that column .

stay MySQL in , Use single INSERT Statements handle multiple insertions rather than using multiple INSERT Faster sentences . When using a single INSERT When a statement inserts multiple rows of data , Just enclose each row of data in parentheses .

Example ： Add values to all fields in the table

stay tb_courses Insert a new record into the table ,course_id The value is 1,course_name The value is “Network”,course_grade The value is 3,info The value is “Computer Network”.

INSERT INTO tb_courses(course_id,course_name,course_grade,course_info)VALUES(1,'Network',3,'Computer Network');

You can see that the record is inserted successfully . When inserting data , It specifies tb_courses All fields of the table , Therefore, a new value will be inserted for each field .

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