At the end of this lesson, you should be able to: Describe each DML statement Insert rows into a table Update rows in a table Delete rows from a table Control transactions

A DML statement is executed when you: Add new rows to a table Modify existing rows in a table Remove existing rows from a table A transaction consists of a collection of DML statements that form a logical unit of work.

Department dept_nbr dept_name location 10 Accounting New York 20 Research Dallas 30 SalesChicago 40 Operations Boston New row 50 Development Detroit Department dept_nbr dept_name location 10 Accounting New York 20 Research Dallas 30 Sales Chicago 40 Operations Boston “…insert a new row into DEPT table…” 50 Development Detroit

Add new rows to a table by using the INSERT statement. Only one row is inserted at a time with this syntax. INSERT INTO table [(column [, column...])] VALUES (value [, value...]); INSERT INTO table [(column [, column...])] VALUES (value [, value...]);

Insert a new row containing values for each column. Optionally list the columns in the INSERT clause. List values in the default order of the columns in the table. Enclose character and date values within single quotation marks. MySQL>INSERT INTO deptartment(dept_nbr, dept_name, location) 2 VALUES (50, 'Development', 'Detroit'); 1 row created.

Implicit method: Omit the column from the column list. Explicit method: Specify the NULL keyword. MySQL>INSERT INTOdepartment (dept_nbr, dept_name ) 2 VALUES(60, 'MIS'); 1 row created. MySQL>INSERT INTOdeptartment 2 VALUES(70, 'FINANCE', NULL); 1 row created.

TheCURDATE function records the current date and time. MySQL> INSERT INTOemployee (employee_nbr, name, job, 2manager, hire_date, salary, 3commission, dept_nbr) 4 VALUES (7196, 'Green', 'Salesman', 57782,CURDATE(), 2000, NULL, 610); 1 row created.

Use multiple INSERT statements. Submit all at once with each statement terminated by a semicolon. MySQL>INSERT INTOdepartment (dept_nbr, dept_name, 2location) 3 VALUES(50, ‘Development’, ‘Detroit’); INSERT INTOdepartment (dept_nbr, dept_name, 2location) 3 VALUES(60, ‘Huntsville’, ‘MIS’);

As long as column names are specified or all data is in the proper order you may OMIT the additional INSERT value clauses. Multiple sets of values require only a single VALUE clause Each set enclosed in parentheses separated by commas. MySQL>INSERT INTOdepartment (dept_nbr, dept_name, 2location) 3 VALUES(50, ‘Development’, ‘Detroit’), 4 VALUES(60, ‘Huntsville’, ‘MIS’);

“…delete a row from DEPT table…” department dept_nbr dept_name location 10 Accounting New York 20 Research Dallas 30 SalesChicago 40 Operations Boston 50 Development Detroit 60 MIS... department dept_nbr dept_name location 10 Accounting New York 20 Research Dallas 30 SalesChicago 40 Operations Boston 60 MIS...

You can remove existing rows from a table by using the DELETE statement. DELETE [FROM] table [WHERE condition]; DELETE [FROM] table [WHERE condition];

Specific row or rows are deleted when you specify the WHERE clause. All rows in the table are deleted if you omit the WHERE clause. MySQL>DELETE FROMdepartment 2 WHERE dept_name = 'Development'; 1 row deleted. MySQL>DELETE FROMdepartment 2 WHERE dept_name = 'Development'; 1 row deleted. MySQL> DELETE FROMdepartment; 4 rows deleted. MySQL> DELETE FROMdepartment; 4 rows deleted.

MySQL>DELETE FROMdepartment 2 WHEREdept_nbr = 10; MySQL>DELETE FROMdepartment 2 WHEREdept_nbr = 10; ERROR 1451: Cannot delete or update a pa……… You cannot delete a row that contains a primary key that is used as a foreign key in another table. Row: a foreign key constraint foils

May contain one of the following statements: DML statements (INSERT, UPDATE, DELETE) that make up one consistent change to the data One DDL statement (CREATE, ALTER, DROP) One DCL statement (GRANT, REVOKE)

Begin with a START TRANSACTION statement End with one of the following events: COMMIT or ROLLBACK DDL or DCL statement executes (automatic commit) Certain errors, exit, or system crash

Ensure data consistency Preview data changes before making changes permanent Group logically related operations

DELETE Transaction Savepoint A ROLLBACK to Savepoint B DELETE Savepoint B COMMIT INSERT UPDATE ROLLBACK to Savepoint A INSERTUPDATE INSERT ROLLBACK INSERT

The previous state of the data can be recovered because the database buffer is affected. The current user can review the results of the DML operations by using the SELECT statement. Other users cannot view the results of the DML statements by the current user. The affected rows are locked; other users cannot change the data within the affected rows.

Data changes are made permanent in the database. The previous state of the data is permanently lost. All users can view the results. Locks on the affected rows are released; those rows are available for other users to manipulate. All savepoints are erased.

Autocommit is the default transaction processing mode in MySQL An automatic commit (database update) occurs under the following circumstances: A DML statement is completed A DDL statement is issued A DCL statement is issued An automatic rollback occurs under an abnormal termination of MySQL or system failure

The default setting may be changed by issuing the following statement: SET autocommit = 0; 0 = false 1 = true Setting the autocommit = 0 instructions the MySQL to not automatically commit changes, unless the flag is set back to true. The autocommit flag is per connection, and NOT server- wide

Make the changes. Commit the changes. MySQL>UPDATEemployee 2 SET dept_nbr = 10 3 WHEREemployee_nbr = 7782; 1 row updated. MySQL>UPDATEemployee 2 SET dept_nbr = 10 3 WHEREemployee_nbr = 7782; 1 row updated. MySQL> COMMIT; Commit complete.

Discard all pending changes by using the ROLLBACK statement. Data changes are undone. Previous state of the data is restored. Locks on the affected rows are released. MySQL> DELETE FROMemployee; 14 rows deleted. MySQL> ROLLBACK; Rollback complete.

Create a marker within a current transaction by using the SAVEPOINT statement. Roll back to that marker by using the ROLLBACK TO SAVEPOINT statement. MySQL> UPDATE... MySQL> SAVEPOINT update_done; Savepoint created. MySQL> INSERT... MySQL> ROLLBACK TO update_done; Rollback complete.

StatementDescription INSERTAdds a new row to the table UPDATEModifies existing rows in the table DELETERemoves existing rows from the table START TRANSACTIONMarks the beginning of explicit transaction processing COMMITMakes all pending changes permanent SAVEPOINTAllows a rollback to the savepoint marker ROLLBACKDiscards all pending data changes SET AUTOCOMMET0 = False (OFF) 1 = True (ON)