mysql check duplicate records code example

Example 1: find duplicates mysql column

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

Example 2: select where duplicate mysql

SELECT 
    col1, COUNT(col1),
    col2, COUNT(col2)
FROM
    table_name
GROUP BY 
    col1, 
    col2
HAVING 
       (COUNT(col1) > 1) AND 
       (COUNT(col2) > 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)

Example 5: 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...;