SQL Chapter 2 Chapter 3

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1： insert data

perhaps

2： Display the data

SELECT * FROM Table name

 

3： Data update

4：WHERE Clause

Comparison operator , determine

 

1： Inquire about

SELECT sentence

2： The only value 、

SELECT DISTINCT Name FROM Table name ;

 

3：WHERE Clause to filter the result

Explain the meaning of the above code

 

4： Logic operation symbol

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

1：AND OR

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

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

 

4：LIKE Operator

LIKE The operator can be followed by a wildcard

5：IN Operation symbol

 

5：ORDER BY Sort

Positive sequence sort

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

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 .