Write IF..ELSE in MYSQL - mysql

Question

I have a table looked like this
mysql> select * from rc;
+----+----------------------------+----------------------------+----------------------------+
| id | business_date | cutoff_dt | recon_dt |
+----+----------------------------+----------------------------+----------------------------+
| 1 | 2017-03-21 16:50:29.032000 | 2017-03-21 16:50:31.441000 | 2017-03-21 16:50:32.832000 |
+----+----------------------------+----------------------------+----------------------------+
1 row in set (0.00 sec)
I want to run query
-Select * from rc where business_date = '2017-03-17'
- ifcutoff_dt` is null or empty, it will display null, otherwise display not null
I wrote it into shell script.
#! /bin/bash
mysql -u root -p <<rcard
use rcard;
SELECT *
(CASE WHEN (cut_off_dt = "NULL")
THEN
echo "Null"
ELSE
echo "NOT NULL"
END)
from rc WHERE business_date = '2017-03-17';
rcard
But I get error
ERROR 1064 (42000) at line 2: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '(CASE WHEN (cut_off_dt = "NULL")
THEN
echo "Null"
ELSE
' at line 2
Is it the correct way to write the IF ELSE in MySQL ?

Answer 1

This is not the correct way to check for NULL values.
Try this:
SELECT *,
IF(mepslog_cut_off_dt IS NULL, 'NULL', 'NOT NULL')
from rc_mepslog
WHERE mepslog_business_date = '2017-03-17';
You can alternatively use a CASE expression:
SELECT *,
CASE
WHEN mepslog_cut_off_dt IS NULL THEN 'NULL'
ELSE 'NOT NULL'
END
from rc_mepslog
WHERE mepslog_business_date = '2017-03-17';

Answer 2

SELECT *, (CASE WHEN (mepslog_cut_off_dt IS NULL)
THEN
'Null'
ELSE
'NOT NULL' END) from rc WHERE business_date = '2017-03-17'
To compare if the value is null, use column IS NULL instead of column = 'NULL'; the latter would check if the column you are comparing has the string 'null'

Answer 3

There's a missing comma after select * and none of your table names you specified in the query exists. To separate a table from the column, you use a dot .. There are other wrong written column names appart from that. Also, you don't use echo, you simply specify what to do. Also, I'd suggest to use an alias for the selected column from the case (AS 'nullOrNotNull')
SELECT * ,
CASE WHEN cut_off_dt IS NULL
THEN
'Null'
ELSE
'NOT NULL'
END AS 'nullOrNotNull'
from rc WHERE business_date = '2017-03-17';