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SQL Chapter 2 Chapter 3
2020-11-09 10:51:00 【osc_ptcuqdug】
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 .
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