2. dml_insert_delete_update

2Manipulating Data in Tables

Ms. Amrit Kaurgamritkaur@live.com

Storing Data in a Table

• The data that you can add in a table is a row.• INSERT Statement is used to add row in a

table.

INSERT INTO tablename [column_list)]VALUES ( {value_list | select_statement})

• Inserting New Data

• Inserting Partial Data

• Copying Data from Existing Table

• Inserting Data Interactively– substitution operator (&) is used for reading data from

keyboard.

Guidelines for Inserting Rows

• The number of data values must be same as the number of columns in the table or column list.

• The order of inserting the information must be same as the order in which columns are listed in table or column list

• The data type of information must match with the data types of the column.

Storing Data Using SubqueriesINSERT INTO table_name [ (column1 [, column2 ]) ] SELECT [ *|column1 [, column2 ] FROM table1[ WHERE search_condition];

UPDATING Data in a Table

• UPDATE statement is use to make changes in an existing row(s).

• We can update one or more than one column of a row.

UPDATE table_nameSET column_name=value [, column_name=value, ...][WHERE condition]

Guidelines for Updating Rows

• An update can be done only one table at a time.

• If an update violates integrity constraints, entire update is rollback.

• If WHERE clause is not used, all rows of a table will be changed to new values.

Updating Data using SubqueriesUPDATE table_name SET column_name = { new_value | [(SELECT [*|column1[,column2

] FROM table_name) ][WHERE condition]

Deleting Data from a Table

• DELETE statement is used to delete row(s) from a table. DELETE FROM table_name

[WHERE search_condition]

• TRUNCATE statement can also be used to delete row(s) from a table.

TRUNCATE TABLE table_name

DELETE vs TRUNCATE

• DELETE is a DML statement whereas TRUNCATE is DDL statement.

• DELETE used to remove rows and WHERE clause is used to remove some rows whereas TRUNCATE command delete all rows

• DELETE operations can be rolled back whereas TRUCATE operation cannot be rolled back.

DELETE vs TRUNCATE

• DELETE will fire trigger whereas No triggers will be fired with TRUNCATE command.

• DELETE does not free the space containing the table whereas TRUNCATE free space containing table and can be used by another table.

Delete Data using SubqueriesDELETE FROM table_name[WHERE column_name operator [(SELECT column_name FROM table_name [ WHERE condition])