当前位置:网站首页>SQL Chapter 2 Chapter 3

SQL Chapter 2 Chapter 3

2020-11-09 10:51:37 osc_ptcuqdug

1: insert data

image.png

perhaps

image.png

2: Display the data

SELECT * FROM Table name

 

3: Data update

image.png

4:WHERE Clause

Comparison operator , determine

 

1: Inquire about

SELECT sentence

image.png

2: The only value 、

SELECT DISTINCT Name FROM Table name ;

 

3:WHERE Clause to filter the result

image.png

image.png

Explain the meaning of the above code

 

4: Logic operation symbol

image.png

The order of the operation levels in the table is from high to low

1:AND OR

image.png

WHERE The operation condition after clause is in accordance with AND>OR The order of

 

2:not Operation symbol

NOT and <> It means the same thing , They are not equal to . Not true .

 

3:BETWEEN Operator

image.png

BETWEEN Specifies a range , The range is between one value and another .

 

4:LIKE Operator

image.png

LIKE The operator can be followed by a wildcard

5:IN Operation symbol

image.png

 

5:ORDER BY Sort

image.png

Positive sequence sort

image.png

Reverse sort

Particular attention , Even if you don't show a row in the table , You can also use this line to sort .

 

6: Selecting data from multiple tables

image.png

image.png

Pay attention to that column , Shows the union of tables .

 

7:NULL data

NULL It means unknown , It's not the same as not having .

 

版权声明
本文为[osc_ptcuqdug]所创,转载请带上原文链接,感谢