Can I add a Unique key on table creation in SQL? - mysql

Question

I am trying to translate a collection of MySQL functions to SQL, and I'm having issues with a UNIQUE KEY issue:
-- -----------------------------------------------------
-- Table testform
-- -----------------------------------------------------
CREATE TABLE `testform` (
`FormId` INT(11) NOT NULL AUTO_INCREMENT,
`TTId` INT(11) NULL DEFAULT NULL,
`TestName` VARCHAR(100) NULL,
PRIMARY KEY (`FormId`),
UNIQUE KEY `TF_Composite` (`TTId`, `TestName`));
When I try and test this in SQLFiddle, it's giving me the error
Incorrect syntax near the keyword 'KEY'.
I have tried searching for this, but so far all I have come up with is "Unique Constraints". Is there a difference between a "Key" and a "Constraint" in SQL? And if so, how can I add this in the table creation statement?

Answer 1

Your syntax is all messed up. Please look at books on-line (MSDN).
https://msdn.microsoft.com/en-us/library/ms174979.aspx
The sample code below create a table in tempdb. This table automatically gets destroyed when the service is restarted.
-- Just a example, throw away after reboot
USE [tempdb]
GO
-- Create the table
CREATE TABLE DBO.TESTFORM
(
FORM_ID INT IDENTITY(1, 1) NOT NULL ,
TT_ID INT NULL,
TEST_NAME VARCHAR(100) NULL,
CONSTRAINT PK_FORM_ID PRIMARY KEY (FORM_ID),
CONSTRAINT UN_COMPOSIT UNIQUE (TT_ID, TEST_NAME)
);
-- Seventies Band
INSERT INTO TEMPDB.DBO.TESTFORM VALUES (1, 'John');
INSERT INTO TEMPDB.DBO.TESTFORM VALUES (2, 'Paul');
INSERT INTO TEMPDB.DBO.TESTFORM VALUES (3, 'Mary');
GO
-- Show data
SELECT * FROM TEMPDB.DBO.TESTFORM
GO
The image below shows the data in this table.

Answer 2

Try This.
CREATE TABLE testform (
FormId INT(11) NOT NULL AUTO_INCREMENT,
TTId INT(11) NULL DEFAULT NULL,
TestName VARCHAR(100) NULL,
PRIMARY KEY (FormId),
CONSTRAINT TF_Composite UNIQUE (TTId,TestName));
More Details..

Answer 3

For Better Understanding about Primary and Unique you can refer below page.
Primary and Unique Key Creation

Answer 4

For MySQL Database
CREATE TABLE `phone` (
`id` MEDIUMINT(8) UNSIGNED NOT NULL AUTO_INCREMENT,
`country` DECIMAL(5,0) UNSIGNED NOT NULL,
`area` DECIMAL(5,0) UNSIGNED NOT NULL,
`number` DECIMAL(8,0) UNSIGNED NOT NULL,
`extension` DECIMAL(5,0) UNSIGNED DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `ix_phone` (`country`, `area`, `number`, `extension`),
) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8;
For alter Table :
ALTER TABLEphone
ADD UNIQUE INDEXix_phone(country,area,number,extension);