Modifying :
Definition: The modify command is used when we have to resize a column in a table. By using this command we have to apply some changes on the result set field. This command allows more or less characters than before.
Syntax :alter table modify
[column name] VARCHAR(5) ;
Also Known As: It also known as the Modify Column, Resize Column into a table in a database.
Examples: alter table people modify name VARCHAR(35);
Add a new column to db.
alter table [table name] add column [new column name] varchar (20);
Delete a column.
alter table [table name] drop column [column
name];
Change column name:
alter table [table name] change [old column name] [new column name] varchar
(50);
Make a unique column so you get no dupes.
alter table [table name] add unique ([column name]);
Make a column bigger.
alter table [table name] modify [column name] VARCHAR(4);
Delete unique from table.
alter table [table name] drop index [column name];
Updating :
It is necessary to change the data in our
database, so these commands are helpful for update a table. Example : UPDATE products SET product_id = 7,
product_name='headphone', c_id=6,price=1201;
To update info already in a table.
UPDATE [table name] SET Select_priv = 'Y',Insert_priv = 'Y',Update_priv = 'Y'
where [field name] = 'user'; Delete a row(s) from a table.
DELETE from [table name] where [field name] = 'something';
Update database permissions/privilages.
FLUSH PRIVILEGES;
Load a CSV file into a table.
LOAD DATA INFILE '/tmp/filename.csv' replace INTO TABLE [table name] FIELDS
TERMINATED BY ',' LINES TERMINATED BY '\n' (field1,field2,field3);