Friday, October 28, 2011
ORACLE SQL TUTORIAL: CASE AND DEFAULT
CASE
Case is similar to
decode but easier to understand while going through coding
Ex:
SQL> Select sal,
Case sal
When 500 then ‘low’
When 5000 then ‘high’
Else ‘medium’
End case
From emp;
SAL CASE
----- --------
500 low
2500 medium
2000 medium
3500 medium
3000 medium
5000 high
4000 medium
5000 high
1800 medium
1200 medium
2000 medium
2700 medium
2200 medium
3200 medium
DEFAULT
Default can be considered as a substitute behavior of not null constraint when applied to new
rows being entered into the table.
When you define a column
with the default keyword followed by
a value, you are actually telling the database that, on insert if a row was not
assigned a value for this column, use the default value that you have
specified.
Default is applied only
during insertion of new rows.
Ex:
SQL> create table student(no number(2) default 11,name varchar(2));
SQL> insert into student values(1,'a');
SQL> insert into student(name) values('b');
SQL> select * from student;
NO NAME
------ ---------
1 a
11 b
SQL> insert into student values(null, ‘c’);
SQL> select * from student;
NO NAME
------ ---------
1 a
11 b
C
-- Default
can not override nulls.
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