Add a field (one column)
ALTER TABLE TABLE_NAME ADD Column Column_name Type Default Value; Type refers to the type of this field, the value refers to the default value of the field.
For example: ALTER TABLE MYBOOK ADD Column Publish_house varchar (10) default ';
2. Change a field name (you can also change the type and default)
ALTER TABLE TABLE_NAME CHANGE SORCE_COL_NAME DEST_COL_NAME TYPE DEFAULT VALUE; source_col_name Refers the original field name, Dest_col_name Remifes the name of the field name
For example: Alter Table Board_info Change Ismobile IstelPhone Int (3) Unsigned Default 1;
3. Change the default value of a field
Alter Table Table_name alter column_name set default value;
For example: ALTER TABLE BOOK ALTER FLAG SET DEFAULT '0';
4. Change the data type of a field
Alter Table Table_name Change Column Column_Name Column_name Type
For example: ALTER TABLE Userinfo Change Column Username Username Varchar (20);
5. Add a column to a table as a primary key
Alter Table Table_name Add Column Column_name Type Auto_Increment Primary Key;
For example: ALTER TABLE BOOK ADD Column ID Int (10) Auto_Increment Primary Key;
6. The backup of the database, entered in the command line:
Mysqldump -u root -p Database_name Table_name> Bak_File_Name
For example: mysqldump -u root -p f_info user_info> user_info.dat
7. Export data
SELECT_STAMENT INTO OUTFILE "dest_file";
For example: Select Cooperatecode, CreateTime from Publish Limit 10 INTO OUTFILE "/HOME / MZC/Temp/tempbad.txt";
8. Import data
Load data infile "file_name" inTo Table Table_name
For example: load data infile "/home/mzc/temp/tempbad.txt" INTO TABLE PAD;
9. Insert the data in both tables to another table. The following example describes that the value of the COM2 in the T1 table is spliced into the field corresponding to the TX table after splicing the value of the COM1 field in the T2 table.
For example: INSERT INTO TX SELECT T1.COM1, Concat (T1.COM2, T2.COM1) from T1, T2;
