sql if else

Question

table

eid Ename departnam

E1 science 2

E2 maths 3

E3 Null 4

E4 english 1

 

 

 in above table

i am table 3 columns,

i need 3 queries should be written in scripts

1. when we search ename other than in table it should display like not exists

2. if u search e3 then it should display as default depatment and ename

3. if u search any name in this table then it should display name and departname

please help