SQL

find duplicates mysql column

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

finding duplicate rows mysql

SELECT varchar_col
FROM table
GROUP BY varchar_col
HAVING COUNT(*) > 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

finding duplicate rows mysql

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

mysql find duplicate rows multiple columns

-- multiple columns
SELECT COUNT(*) c , 
CONCAT(students.first_name, "----",students.last_name) 
FROM students WHERE students.class_id = classes.id
GROUP BY CONCAT(first_name,"----",last_name) HAVING c > 1;

Mysql Selected All Duplicate Rows

select t.*
from table t
where exists (select 1 from table t2 where t2.url = t.url and t2.id <> t.id);