SELECT
t1.primary_id,
t1.duplicate_id,
t1.data1,
t1.data2
FROM
table_name t1
LEFT JOIN table_name t2
ON (t1.duplicate_id = t2.duplicate_id AND t1.primary_id < t2.primary_id)
WHERE
t2.primary_id IS NULL
## 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
-- 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;
SELECT firstname,
lastname,
list.address
FROM list
INNER JOIN (SELECT address
FROM list
GROUP BY address
HAVING COUNT(id) > 1) dup
ON list.address = dup.address;
-- You can duplicate or "clone" a table's contents by executing
> CREATE TABLE new_table AS SELECT * FROM original_table;
-- keep in mind that new new_table inherits ONLY the basic column definitions, null settings
-- and default values of the original_table. It does not inherit indexes and auto_increment
-- definitions.
-------------------------------------------------------------------------------------------
-- To inherit all table definitions
> CREATE TABLE new_table LIKE original_table; -- copy table structure only
> INSERT INTO new_table SELECT * FROM original_table; -- add data from old table
SELECT firstname,
lastname,
list.address
FROM list
INNER JOIN (SELECT address
FROM list
GROUP BY address
HAVING COUNT(id) > 1) dup
ON list.address = dup.address;