SQL Update statement
We can update existing records in a tables using UPDATE statement.
Example:
UPDATE table_name
SET column1=value, column2=value2,...
WHERE some_column=some_value
SET column1=value, column2=value2,...
WHERE some_column=some_value
Note: if you dont use where clause, it will update all records in a table.
Update Example:
Now we will update records in following table
| ID | Category | Author | Tutorial |
| 1 | PHP | Hassan | what is php |
| 2 | MySql | James | what is sql |
| 3 | Ajax | Andrew | what is ajax |
| 4 | ASP | James | ASP Introduction |
| 5 | C++ | Andrew | C++ Basics |
| 7 | CSS | Williams |
update tutorials set tutorial='css introduction' where id =7
It will show following results.
| ID | Category | Author | Tutorial |
| 1 | PHP | Hassan | what is php |
| 2 | MySql | James | what is sql |
| 3 | Ajax | Andrew | what is ajax |
| 4 | ASP | James | ASP Introduction |
| 5 | C++ | Andrew | C++ Basics |
| 7 | CSS | Williams | css introduction |
Note: I have hilight 'css introduction' in red color because it has updated with above mentioned query.
Be careful when updating records. If we had omitted the WHERE clause in the example above, like this:
update tutorials set tutorial='css introduction'
It will show following results.
| ID | Category | Author | Tutorial |
| 1 | PHP | Hassan | css introduction |
| 2 | MySql | James | css introduction |
| 3 | Ajax | Andrew | css introduction |
| 4 | ASP | James | css introduction |
| 5 | C++ | Andrew | css introduction |
| 7 | CSS | Williams | css introduction |
We can also use update statement with multiple columns like
update tutorials set tutorial='css introduction', author='kashif', where id =7
