Question

1. How to swap the same columns value ?

table_name

id    value

1      0

2      1

3      0

4      1

How to Change the values 0 to 1 and 1 to 0 using mysql query?

1. How to print the following o/p ?

table_name

id name

1   x

2   y

3   NULL

If the name contains value it should print as “Hi X” else if the name is NULL it should print as “Hello Guest”.

My O/P should be like below

name

Hi X

Hi y

Hello Guest

How can this be done ?

Thanks in advance….

Answer 1

1)

You can simply do:

SELECT id, NOT value AS value
FROM tbl

NOT will switch 0 to 1 and vice versa.

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2)

You can use COALESCE() in conjunction with CONCAT():

SELECT COALESCE(CONCAT('Hi ', name), 'Hello Guest') AS name
FROM tbl

—

• If at least one item in CONCAT() is NULL, then CONCAT() will return NULL regardless of any other item in its parameters.

• COALESCE() outputs the first non-NULL parameter.

—

So if name is NULL, then CONCAT() will return NULL, and COALESCE() will output Hello Guest instead.