I know MSSQL very well. But when trying some basic things of SQL in Oracle I am getting in trouble. Tried to search on other sites but didn't found proper + simple example. 
Suppose I have SQL statements as follows

```
Declare @mID int = 45
Select * from MyTable where id= @mID

```

I tried to write same code in Oracle (SQL Developer). But it didn't worked.

```
Declare 
mID number := 45
Begin
Select * from MyTable where id= mID
End;

```

Actually, I tried some more statements but didn't executed. All I got was ERRORS.
Can anyone come up with simple & correct solution?