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2. DML_INSERT_DELETE_UPDATE

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2. DML_INSERT_DELETE_UPDATE

  1. 1. Manipulating Data in Tables Ms. Amrit Kaur gamritkaur@live.com
  2. 2. 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})
  3. 3. • Inserting New Data • Inserting Partial Data • Copying Data from Existing Table • Inserting Data Interactively – substitution operator (&) is used for reading data from keyboard.
  4. 4. 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.
  5. 5. Storing Data Using Subqueries INSERT INTO table_name [ (column1 [, column2 ]) ] SELECT [ *|column1 [, column2 ] FROM table1 [ WHERE search_condition];
  6. 6. 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_name SET column_name=value [, column_name=value, ...] [WHERE condition]
  7. 7. 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.
  8. 8. Updating Data using Subqueries UPDATE table_name SET column_name = { new_value | [(SELECT [*|column1[,column2 ] FROM table_name) ] [WHERE condition]
  9. 9. 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
  10. 10. 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.
  11. 11. 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.
  12. 12. Delete Data using Subqueries DELETE FROM table_name [WHERE column_name operator [(SELECT column_name FROM table_name [ WHERE condition])

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