Updating a specific row in sql
When updating your table, the WHERE clause is crucial, although by default in My SQL it is set to be optional.If you don’t provide a WHERE condition, all rows of the table will be updated.Nevertheless, nothing would have happened – the statement would have worked, affecting 0 rows, because the data table doesn’t contain an employee with such a number at the moment of the query’s execution.Stay focused for another interesting feature we will discuss next.It will refer to the state corresponding to the time you executed COMMIT.This means if you have already used COMMIT 10 times, ROLLBACK will have an effect on the last execution you have performed.
Note that we did not update the “hire date” column value, right? This is fine, as we do not have to update each value of the record of interest. With a different birthdate and gender, although with the same hire date.One can always make a simple mistake that could result in the loss of a large amount of data. One last thing – to properly switch off the safe updates, reconnection to the database is required. It is used to update the values of existing records in a table.So, let’s exit this connection and then reconnect, typing the password once again! In the previous post about SQL INSERT Statement, we inserted an employee under the number of 9-9-9-9-0-1, remember? The syntax to adhere to is UPDATE table name, the keyword SET, column names and the respective values assigned to them, and finally – WHERE, and a certain condition, or set of conditions, that must be satisfied.After that moment, even if you run the ROLLBACK clause 20 times, you can get to the state of only the last COMMIT.You cannot restore data to a state corresponding to an earlier COMMIT.