Case statement in MySQL

I have a database table called '**tbl_transaction**' with the following definition:

id INT(11) Primary Key
action_type ENUM('Expense', 'Income')
action_heading VARCHAR (255)
action_amount FLOAT

I would like to generate two columns: `Income Amt` and `Expense Amt`.

Is it possible to populate the columns conditionally, using only a SQL Query, such that the output appears in the correct column, depending on whether it is an Expense item or an Income item?

For example:

ID Heading Income Amt Expense Amt
1 ABC 1000 -
2 XYZ - 2000


I'm using MySQL as the database. I'm trying to use the CASE statement to accomplish this.

Cheers!

Try to use `IF(condition, value1, value2)`

SELECT ID, HEADING,
IF(action_type='Income',action_amount,0) as Income,
IF(action_type='Expense',action_amount,0) as Expense

This should work:

select
id
,action_heading
,case when action_type='Income' then action_amount else 0 end
,case when action_type='Expense' then expense_amount else 0 end
from tbl_transaction

MySQL also has `IF()`:

SELECT
id, action_heading,
IF(action_type='Income',action_amount,0) income,
IF(action_type='Expense', action_amount, 0) expense
FROM tbl_transaction

Yes, something like this:

SELECT
id,
action_heading,
CASE
WHEN action_type = 'Income' THEN action_amount
ELSE NULL
END AS income_amt,
CASE
WHEN action_type = 'Expense' THEN action_amount
ELSE NULL
END AS expense_amt

FROM tbl_transaction;

---

As other answers have pointed out, MySQL also has the `IF()` function to do this using less verbose syntax. I generally try to avoid this because it is a MySQL-specific extension to SQL that isn't generally supported elsewhere. `CASE` is standard SQL and is much more portable across different database engines, and I prefer to write portable queries as much as possible, only using engine-specific extensions when the portable alternative is *considerably* slower or less convenient.

Another thing to keep in mind is there are two different CASEs with MySQL: one like what @cdhowie and others describe here (and documented here:

[To see links please register here]

) and something which is called a CASE, but has completely different syntax and completely different function, documented here:

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Invariably, I first use one when I want the other.

I hope this would provide you with the right solution:

Syntax:

CASE
WHEN search_condition THEN statement_list
[WHEN search_condition THEN statement_list]....
[ELSE statement_list]
END CASE

Implementation:


select id, action_heading,
case when
action_type="Expense" then action_amount
else NULL
end as Expense_amt,
case when
action_type ="Income" then action_amount
else NULL
end as Income_amt
from tbl_transaction;


Here I am using `CASE` statement as it is more flexible than `if-then-else`. It allows more than one branch. And `CASE` statement is standard SQL and works in most databases.