duplicate check in mysql code example

Example 1: find duplicates mysql column

SELECT name, COUNT(*) c FROM table GROUP BY name HAVING c > 1;

Example 2: find duplicate keys in mysql

SELECT col, COUNT(col) FROM table_name GROUP BY col HAVING COUNT(col) > 1;

Example 3: 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 4: MySQL repeated values

SELECT 
    col, 
    COUNT(col)
FROM
    table_name
GROUP BY col
HAVING COUNT(col) > 1;
Code language: SQL (Structured Query Language) (sql)