SQL

sql query to find duplicates in column

SELECT name, COUNT(email) 
FROM users
GROUP BY email
HAVING COUNT(email) > 1

duplicate column values sql

-- copy values from old column to new column
UPDATE tablename SET new_column = old_column

how to get duplicate values in sql

• SELECT first_name, COUNT (first_name) FROM employees
GROUP BY first_name
HAVING (COUNT(first_name) > 1);

sql check duplicate value in column

SELECT columnName, COUNT(columnName)
FROM tableName
GROUP BY columnName
HAVING COUNT(columnName)>1

sql find duplicate records in two tables

SELECT  *   
FROM TableA A  
WHERE NOT EXISTS (SELECT *      
                  FROM TableB B
                  WHERE A.NUM = B.NUM);

FIND DUPLICATES IN COLUMN SQL

declare @YourTable table (id int, name varchar(10), email varchar(50))

INSERT @YourTable VALUES (1,'John','John-email')
INSERT @YourTable VALUES (2,'John','John-email')
INSERT @YourTable VALUES (3,'fred','John-email')
INSERT @YourTable VALUES (4,'fred','fred-email')
INSERT @YourTable VALUES (5,'sam','sam-email')
INSERT @YourTable VALUES (6,'sam','sam-email')

SELECT
    name,email, COUNT(*) AS CountOf
    FROM @YourTable
    GROUP BY name,email
    HAVING COUNT(*)>1

duplicate a column in sql

ALTER TABLE Table1
ADD SubCategory2 {Type of subcategory 1} {NULL|NOT NULL} 
UPDATE Table1 SET SubCategory2 = SubCategory;