-
7/27/2019 Dml in Mysql
1/3
DML Statement in MySQL
Data Manipulation Language (DML) statements are used for
managing data within
schema objects (e.g. table). It includes Inserting, Updating and
deleting of data.
Inserting Data into Tables:
INSERT statement allows you to insert one or more rows to the
table.
INTO clause in the INSERT statement is optional.
It is possible to write the INSERT INTO statement in two
forms.
The first form doesn't specify the column names where the data
will be inserted, only their
values. It is used where users need to insert values to all
available columns of a table.
Syntax:
mysql> INSERT INTO table_name
VALUES (value1, value2, value3,...);
Example:
mysql> INSERT INTO student
VALUES (1,'Ajay','Hyderabad');
The second form specifies both the column names and the values
to be inserted. It is used
where users need to insert value to specific column(s) of a
given table.
Syntax:
mysql> INSERT INTO table_name (column1, column2,
column3,...) VALUES (value1, value2, value3,...)
Example:
mysql> INSERT INTO student (Rollno, Name)
VALUES (2, 'Rahul');
In another form, instead of providing explicit data, you select
it from other table by using
SELECT statement. This form allows you to copy all or some part
of data from other table to the
inserted table.
-
7/27/2019 Dml in Mysql
2/3
As an example, we can create a temporary table and insert all
offices which locate in US
into that one by using this query:
mysql> INSERT INTO temp_table SELECT * FROM offices WHERE
country = US;
Updating Data in Tables:
SQL UPDATE statement is used to update existing data in database
tables. It can be used
to change values of single row, group of rows or even all rows
in a table.
Followed by the UPDATE keyword is the name of a table you want
to change the data. If
an UPDATE command violates any integrity constraint, MySQL does
not perform the update
and it will issue an error message.
The SET clause determines the column(s) name and the changed
value(s). The changed
values could be a constant value, expression or even a
subquery.
WHERE clause determines which rows of the tables will be
updated. It is an optional part
of SQL UPDATE statement. If WHERE clause is ignored, all rows in
the tables will be updated.
In employees table, if you want to update the email of Mary with
employeeid 1 with the
new email as [email protected], you can execute the
following query.
mysql> UPDATE employees SET email
[email protected]
WHERE employeeid = 1;
The following syntax will update the email of all employees with
the new email as
[email protected].
mysql> UPDATE employees SET email
[email protected];
Deleting Records from Tables:
The DELETE FROM statement is used to delete records from a
database table. TheWHERE clause in DELETE statement specifies
condition to limit which rows you want to
remove.If a record meets WHERE condition, it will be removed
from the database table
permanently. If the WHERE clause is ignored in the MySQL DELETE
statement, all rows of thetable are deleted.
-
7/27/2019 Dml in Mysql
3/3
Suppose you want to delete all employees in an office with
officeNumber is 4, just execute
the following query:
mysql> DELETE FROM employees WHERE officeCode = 4;
To delete all employees from all offices, just remove the WHERE
condition as follows:
mysql> DELETE FROM employees;
