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SQL replace query to substitute part of field data |
We know how to change data inside a field by using update command inside a query. Here we will try to learn how to replace part of the data without changing the entire data of the field. The SQL query we design will work like string replacement in any script we use. For this we will use replace command to replace a part of the data inside a field. Let us try to learn this with an example.
In one employee table ( name emp ) we have three fields, name designation and department. There are different designation given based on the name of their department like GM( finance ), Manager (HR), VP(Sales) etc. Now let us say that the department name Sales changed to Marketing in the organization. We can give a single update command in the field department to change the department name to Marketing where ever it is Sales. But the problem is changing the designation of GM( Sales ) to GM ( Marketing), the query should change only for 'Sales' inside department field and should not change their main designation like GM, VP or Manager. It should only change part of the designation saying about the particular function ( or department ).
Here is the table before any changes are applied.
| name |
designation |
department |
| JOhn D |
GM(Sales) |
Sales |
| Nill K |
GM(Finance) |
Finance |
| Poul P |
VP(Sales) |
Sales |
| Kriss A |
VP(HR) |
HR |
| Ricky T |
Manager(Sales) |
Sales |
| Rolls N |
Manager(IT) |
IT |
Now we will try to change the departments exists within the designation field. Before that let us change the department name to Marketing by using this simple update command.
update emp set department='Marketing' where department='Sales'
The output of this query is shown below
| name |
designation |
department |
| JOhn D |
GM(Sales) |
Marketing |
| Nill K |
GM(Finance) |
Finance |
| Poul P |
VP(Sales) |
Marketing |
| Kriss A |
VP(HR) |
HR |
| Ricky T |
Manager(Sales) |
Marketing |
| Rolls N |
Manager(IT) |
IT |
In the above table, we can see the department name is changed. Now we have to apply replace query to change the department part of the designation field. The field data saying Manger( Sales) should change to Manager( Marketing) and Manager ( HR) should not change. Now here is the query
UPDATE emp set designation=replace(designation, 'Sales', 'Marketing') where department='Marketing'
The output of this query is shown below
| name |
designation |
department |
| JOhn D |
GM(Marketing) |
Marketing |
| Nill K |
GM(Finance) |
Finance |
| Poul P |
VP(Marketing) |
Marketing |
| Kriss A |
VP(HR) |
HR |
| Ricky T |
Manager(Marketing) |
Marketing |
| Rolls N |
Manager(IT) |
IT |
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