Get duplicates values from values table

Create table
CREATE TABLE IF NOT EXISTS `emp1` (
`first_name` varchar(20) NOT NULL,
`last_name` varchar(20) NOT NULL
)

Insertion

INSERT INTO `emp1` (`first_name`, `last_name`) VALUES (‘roy’, ‘raj’), (‘joy’, ‘josh’);

SELECT `first_name`
FROM emp1
GROUP BY `first_name`
HAVING COUNT(*) = N

Change the HAVING condition to >=2
It outputs roy and joy are duplicates having more then one record wirh same value.

Change the HAVING condition to >1 to list non duplicate values, etc

INSERT IGNORE

Create table
CREATE TABLE IF NOT EXISTS `emp` (
`first_name` varchar(20) NOT NULL,
`last_name` varchar(20) NOT NULL,
PRIMARY KEY (`last_name`)
)

Insertion
INSERT INTO `emp` (`first_name`, `last_name`) VALUES (‘roy’, ‘raj’), (‘joy’, ‘josh’);

Useful Queries

INSERT IGNORE
If a record doesn’t have duplicate date then MySql inserts usual.
If a record have duplicate data, the IGNORE keyword instructs MySql to discard it with out generating any error message.

INSERT IGNORE INTO `emp` (`first_name`, `last_name`) VALUES (‘roy’, ‘raj’);

here insertion is failed but it won’t shows any error message.

INSERT INTO `emp` (`first_name`, `last_name`) VALUES (‘joy’, ‘raj’);

Here Mysql insertion is failed because here record is duplicate so MySql generate some error like.
#1062 – Duplicate entry ‘raj’ for key ‘PRIMARY

Sitepoint's twitaway experience for choosing right MySQL engine

Hi All,

Posting after a two month break sorry busy with new addition to our family my daughter(Manha). Here we go:

There is an interesting article about the experience Sitepoint developers had with twitaway application while distributing Free PDF who followed them. How they found the importance of choosing right MYSQL engine is how important :) please go through the full article for more details.

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