What Happens If Unique Value Constraints Are Violated

Q

What Happens If Unique Value Constraints Are Violated? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements

✍: FYIcenter.com

A

If you are inserting a new record that has values violating a unique constraint, you will get an error. Note that primary key column has a unique value constraint by default. The following tutorial exercise gives you some good examples:

mysql> INSERT INTO fyi_links (url) VALUES ('www.other.com');
ERROR 1062 (23000): Duplicate entry '0' for key 1

mysql> INSERT INTO fyi_links VALUES (101, 
  'sql.fyicenter.com', 
  NULL,
  0,
  '2006-04-30');
ERROR 1062 (23000): Duplicate entry '101' for key 1

2007-05-11, 5317👍, 0💬

What Happens If Unique Value Constraints Are Violated
What Happens If Unique Value Constraints Are Violated? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If you are inserting a new record that has values violating a unique constraint, you will get an error. Note that primary key column has a unique value constraint by default. ... 2007-05-11, 5318👍, 0💬

How To Use Existing Values in UPDATE Statements
How To Use Existing Values in UPDATE Statements? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If a row matches the WHERE clause in a UPDATE statement, existing values in this row can be used in expressions to provide new values in the SET clause. Existing values are represen... 2007-05-11, 5187👍, 0💬

Is the Order of Columns in the SET Clause Important
Is the Order of Columns in the SET Clause Important? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements Yes. The order of columns in the SET clause of the UPDATE statement is important. There is a BIG DIFFERENCE between MySQL and Oracle on update columns with previous values: Orac... 2007-05-11, 5129👍, 0💬

How To Update Values on Multiple Rows
How To Update Values on Multiple Rows? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If the WHERE clause in an UPDATE matches multiple rows, the SET clause will be applied to all matched rows. This rule allows you to update values on multiple rows in a single UPDATE statement... 2007-05-11, 5097👍, 0💬

How To Update Values in a Table
How To Update Values in a Table? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If you want to update some values in one row or multiple rows in a table, you can use the UPDATE statement. The tutorial script below shows a good example: mysql> UPDATE fyi_links SET counts = 999,... 2007-05-11, 5068👍, 0💬

How To Specify Default Values in INSERT Statement
How To Specify Default Values in INSERT Statement? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If a column is defined with a default value in a table, you can use the key word DEFAULT in the INSERT statement to take the default value for that column. The following tutorial ... 2007-05-11, 5041👍, 0💬

How To Insert a New Row into a Table
How To Insert a New Row into a Table? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements To insert a new row into a table, you should use the INSERT INTO statement with values specified for all columns as shown in the following example: mysql> INSERT INTO fyi_links VALUES (101, 'd... 2007-05-11, 5033👍, 0💬

What Are DML Statements
What Are DML Statements? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements DML (Data Manipulation Language) statements are statements to change data values in database tables. The are 3 primary DML statements: INSERT - Inserting new rows into database tables. UPDATE - Updating ex... 2007-05-11, 4995👍, 0💬

How To Insert Multiple Rows with One INSERT Statement
How To Insert Multiple Rows with One INSERT Statement? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If you want to insert multiple rows with a single INSERT statement, you can use a subquery instead of the VALUES clause. Rows returned from the subquery will be inserted the t... 2007-05-11, 4986👍, 0💬

All rights in the contents of this web site are reserved by the individual author. fyicenter.com does not guarantee the truthfulness, accuracy, or reliability of any contents.