mysql check duplicate before insert code example

Example 1: mysql find duplicates in same table

## Find ALL duplicate recods by value (without grouping them by value) ##
# to find the duplicate, 
# replace all instances of tableName with your table name
# and all instances of duplicateField with the field name where you look for duplicates
SELECT t1.*
FROM tableName AS t1
INNER JOIN(
	SELECT duplicateField
	FROM tableName
	GROUP BY duplicateField
	HAVING COUNT(duplicateField) > 1
)temp ON t1.duplicateField = temp.duplicateField
order by duplicateField

Example 2: duplicate row mysql

# Duplicate row and change values in the duplicated row
INSERT INTO table (col1, col2, col3)
# manually insert data to the duplicated row
SELECT "new value", "new value", "new value" FROM table
WHERE something...;