SQL UPDATE

The SQL commands (UPDATE and DELETE) are used to modify the data that is already in the database. The SQL DELETE command uses a WHERE clause.

SQL UPDATE statement is used to change the data of the records held by tables. Which rows is to be update, it is decided by a condition. To specify condition, we use WHERE clause.

The UPDATE statement can be written in following form:

UPDATE table_name SET [column_name1= value1,... column_nameN = valueN] [WHERE condition]

Let's see the Syntax:

UPDATE table_name
SET column_name = expression
WHERE conditions

Let's take an example: here we are going to update an entry in the source table.

SQL statement:

UPDATE students
SET User_Name = 'beinghuman'
WHERE Student_Id = '3'

Source Table:

See the result after updating value:

Updating Multiple Fields:

If you are going to update multiple fields, you should separate each field assignment with a comma.

SQL UPDATE statement for multiple fields:

UPDATE students
SET User_Name = 'beserious', First_Name = 'Johnny'
WHERE Student_Id = '3'

Result of the table is given below:

MYSQL SYNTAX FOR UPDATING TABLE:

UPDATE table_name
SET field1 = new-value1, field2 = new-value2,
[WHERE CLAUSE]

SQL UPDATE SELECT:

SQL UPDATE WITH SELECT QUERY:

We can use SELECT statement to update records through UPDATE statement.

SYNTAX:

UPDATE tableDestination
SET tableDestination.col = value
WHERE EXISTS (
SELECT col2.value
FROM  tblSource
WHERE tblSource.join_col = tblDestination. Join_col
AND  tblSource.Constraint = value)

You can also try this one -

UPDATE 
Table 
SET
Table.column1 = othertable.column 1,
Table.column2 = othertable.column 2
FROM 
Table
INNER JOIN
Other_table
ON
Table.id = other_table.id

My SQL SYNTAX:

If you want to UPDATE with SELECT in My SQL, you can use this syntax:

Let's take an example having two tables. Here,

First table contains -

Cat_id, cat_name,

And the second table contains -

Rel_cat_id, rel_cat_name

SQL UPDATE COLUMN:

We can update a single or multiple columns in SQL with SQL UPDATE query.

SQL UPDATE EXAMPLE WITH UPDATING SINGLE COLUMN:

UPDATE students
SET student_id = 001
WHERE student_name = 'AJEET';

This SQL UPDATE example would update the student_id to '001' in the student table where student_name is 'AJEET'.

SQL UPDATE EXAMPLE WITH UPDATING MULTIPLE COLUMNS:

To update more than one column with a single update statement:

UPDATE students
SET student_name = 'AJEET',
Religion = 'HINDU'
WHERE student_name = 'RAJU';

This SQL UPDATE statement will change the student name to 'AJEET' and religion to 'HINDU' where the student name is 'RAJU'.