MySQL empties table data

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Clear the table data There are three ways

1 、truncate ( fast ) The auto increment field is cleared from 1 Start Empty the whole table first

2、drop Delete table directly … Nothing, nothing … … … …

3、delete Slow batch The auto increment field is not empty

MySQL Clear table data command ：truncate

explain ： Delete content 、 Free space without deleting definition , That is, the structure of the data table is still . And drop The difference is , It just empties the table data , It's gentle .

truncate table  Table name 

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Be careful ：

Cannot be associated with where Use it together . truncate Deleting data is not allowed rollback Of . truncate After deleting the data, it will reset Identity（ Identity column 、 Self increasing field ）, It is equivalent to that the auto increment column will be set to the initial value , Again from 1 Start recording , Instead of following the original ID Count . truncate Do not write to the server after deleting data log, The overall deletion speed is fast . truncate Do not activate after deleting data trigger( trigger ).

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MySQL Delete table command ：drop

explain ： Delete content and definition , Release space . To put it simply, take out the whole table . It is impossible to add new data in the future , Unless a new table is added .

drop table  Table name ;

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Or is it Add conditions

drop table if exists  Table name 

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Be careful ：

drop Not only clear the table data, but also delete the table structure .

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MySQL Syntax for clearing the contents of the data table ：delete

explain ： Deleting content does not delete definition , Don't free up space . among ,delete table tb Although it is also to delete the data of the whole table , But the process is painful ( The system deletes... Line by line , More efficient truncate low ).

delete from  Table name  where id='1';

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Or is it Without conditions

delete from  Table name ;

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Be careful ：

delete meaning ： Which table data do you want to delete ? Which lines do you want to delete ? delete You can delete a line , You can also delete multiple lines ; If not where Conditions , Delete all data in the table , It's very dangerous ！ This is not recommended ！

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