CRUD DML is the recording operation of the table
First, add data
Syntax:
insert into table [Field Name] values [field value]
Table Name: Indicates add data to the table goes on
(Field name 1, field name 2, ...): Which field to give the value
values (value 1, value 2, ...): setting a specific value
1, all of the fields inserted
① all field names written down
INSERT INTO table name (field 1, field name 2, 3 ... field name) the VALUES (value 1, value 2 and value 3);
② not write the field names, field names by default all
INSERT INTO table name VALUES (value 1, value 2 and value 3, ...);
2, the data insertion portion
INSERT INTO table name (field 1, field name 2, ...) the VALUES (value 1, value 2, ...);
Tips : Adding data field does not use NULL
3 Notes
① inserted data to be same as the data type of the field
② If you do not define a column name after the table name, the default is to add value for all columns
③ In addition to the digital type, other types require the use of quotation marks (single or double quotation marks) due to
④ size of data to be within the predetermined range of the column, such as: the length can not be placed in a length 20 of column 10.
⑤ specified column or not null, null values represent insertion
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Second, modify data
Syntax :
set update table column name = value [where Conditional Expression];
update table: the table name needs to be updated
set: modify column values
where: qualifying record is updated
1, without modifying the condition data (to modify all rows)
update table set field = value;
2, conditional modification data
update table set field where field name = value = value;
Third, delete data
Syntax :
DELETE FROM table [WHERE conditional expression]
If no where clause, all records MySQL table will be deleted, you can specify any condition in the where clause.
1, delete data without conditions
delete from 表名;
2, conditional deletion of data
delete from table where field = value;
3, delete all records truncate table
truncate table 表名;
4, the difference between truncate and delete
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- truncate table table name - is recommended, a structure corresponding to delete the table, and then create a different table.
- delete from table - Delete all records, not recommended, how many records how many times the delete operation is executed.
- truncate table table name - is recommended, a structure corresponding to delete the table, and then create a different table.