Tag: Oracle SQL

Data Development, Database Administration, Databases, SQL August 10, 2023

SQL Tips: How to rename a column in a table – Oracle database – Oracle SQL

At times you will need to change the name of a column in an existing table. If you are not changing the data type, it is just one statement / step that needs to be executed. However, I strongly recommend that you also do a backup step, especially if you’re making the change in a production environment, just in case of an unexpected issue.

If you choose to do the backup, you may perform this with a “create-table-as-select” statement in this form:

create table [table_name_backup] as select * from [table_name];

Here is an example of the above statement:

create table EMPLOYEES_BKUP as select * from EMPLOYEES;

Now that the table you are modifying is all backed up, you can proceed to rename the column.

The rename SQL statement would take this form:

alter table [table_name] rename column [existing_column_name] to [new_column_name];

An example of the statement:

alter table EMPLOYEES rename column SEX to GENDER;

Thanks for reading! I hope you found this information useful.

Data Development, SQL July 3, 2023July 2, 2023

SQL Tips: How to replace a character or a part of a string in a column value – Oracle SQL

If you frequently work with data, you will occasionally need to replace a part of the values in a column for some reason. In our case, we recently had some data that was loaded into a table from a file source and all the values had an unwanted leading and trailing tab character.

We needed to remove these tabs and preferably without resourcing and reloading the data. The solution was to use the REPLACE SQL function.

This is the form of the UPDATE statement that uses the REPLACE function

Update TABLENAME Set COLUMN_TO_BE_UPDATED = REPLACE(COLUMN_TO_BE_UPDATED, ‘Char_or_String_to_replace_in_column_values’, ‘Char_or_String_to_replace_it_with’);

Here is an example that replaces the long street names in the ADDRESS column with their abbreviated corresponding name:

update EMPLOYEE set ADDRESS = REPLACE(ADDRESS, ‘Street’, ‘St’ ), ADDRESS = REPLACE(ADDRESS, ‘Avenue’, ‘Ave’ ), ADDRESS = REPLACE(CITY, ‘Circle’, ‘Cir’ ) where COUNTRY = ‘United States’;

To solve the issue we had, the SQL statement below was used to update the EMPLOYEE column values by replacing the tab character with NULL – as shown below.

Important Note: Before making any major updates to a table, it’s a best practice to back up the table first.

update EMPLOYEE_EXPENSE_DATA set EMPLOYEE = REPLACE(EMPLOYEE, ‘ ‘, NULL) where EMPLOYEE like ‘ %’;

Important Note: Verify your update before you commit the changes.

We repeated this SQL for each column that had the “bad” (unwanted leading and trailing tabs) values.

Thanks for reading! I hope you found this information useful.