Need help in simple SQL

[saurav99990]

I want to replace the content of a column in database. I know I should use this :

CREATE OR REPLACE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE condition

 

but I want to do it without any condition. I want only 1 value in my column that's why I am using replace. Does anyone know to do this? If you are not able to understand my question come on teamviewer....I'll explain you. 

[Psycho]

Huh? I am not understanding you. What do you mean you only want one value? Are there multiple values per record (e.g. comma separated string) or are you saying you want the exact same value for every record?

[saurav99990]

We use (INSERT INTO) to insert a record in the table which creates more than one record when used again. Is there any way to add a record and alternately replacing the prevoius one without adding any new record. I know this would work:

UPDATE Customers
SET ContactName='Alfred Schmidt', City='Hamburg'
WHERE CustomerName='Alfreds Futterkiste';

 

But what if there is no condition ie. we don't know the record, we only know the column name. Is there any way to fill only one record and alternately replace the previous record without creating 2nd record?

[cyberRobot]

You could test for the existence of a record before inserting a new record. If one exists, use update. Otherwise, use insert.

[Psycho]

@cyberRobot, that method is not recommended as it can still lead to duplicates due to race conditions.

 

@saurav99990,

 

There is a simple solution: ON DUPLICATE KEY UPDATE. You would need to set a UNIQUE constraint on the appropriate field - in your example it would be "CustomerName". Then you just create an INSERT query with an optional ON DUPLICATE condition.

 

 

INSERT INTO Customers
   (CustomerName, ContactName, City)
VALUES
    ('Alfreds Futterkiste', 'Alfred Schmidt', 'Hamburg') '<< Only provide data on this line
ON DUPLICATE KEY UPDATE
    SET ContactName = VALUES(ContactName),
    SET City = VALUES(City)

 

If a record with the CustomerName 'Alfreds Futterkiste' does not exist, a new record is created with the values for CustomerName, ContactName & City. If a record with that CustomerName does exist, then the fields for ContactName & City will be updated (if the values are different than what exists for the field currently)