The only statements allowed directly in pl/sql are DML and TCL.
BINDING
Binding a variable is the process of identifying the storage location associated with an identifier in the program.
Types of binding
Ø Early binding
Ø Late binding
Ø Binding during the compiled phase is early binding.
Ø Binding during the runtime phase is late binding.
Ø In early binding compile phase will take longer because of binding work but the execution
is faster.
Ø In late binding it will shorten the compile phase but lengthens the execution time.
Ø Pl/sql by default uses early binding.
Ø Binding also involves checking the database for permissions to access the object
Referenced.
DYNAMIC SQL
If you use DDL in pl/sql it validates the permissions and existence if requires during compile time which makes invalid.
We can avoid this by using Dynamic SQL.
Dynamic SQL allows you to create a SQL statement dynamically at runtime.
Two techniques are available for Dynamic SQL.
Ø Native Dynamic SQL
Ø DBMS_SQL package
USING NATIVE DYNAMIC SQL
Using execute immediate
Begin
Execute immediate ‘create table student(no number(2),name varchar(10))’;
or
Execute immediate (‘create table student(no number(2),name varchar(10))’);
End;
Using execute immediate with pl/sql variables
declare
v varchar(100);
begin
v := 'create table student(no number(2),name varchar(10))';
execute immediate v;
end;
Using execute immediate with bind variables and using clause
declare
v varchar(100);
begin
v := 'insert into student values(:v1,:v2,:v3)';
execute immediate v using 6,'f',600;
end;
Executing queries with open for and using clause
create or replace procedure p(smarks in number) is
s varchar(100) := 'select *from student where marks > :m';
type t is ref cursor;
c t;
v student%rowtype;
begin
open c for s using smarks;
loop
fetch c into v;
exit when c%notfound;
dbms_output.put_line('Student Marks = ' || v.marks);
end loop;
close c;
end;
Queries with execute immediate
declare
d_name dept.dname%type;
lc dept.loc%type;
v varchar(100);
begin
v := 'select dname from dept where deptno = 10';
execute immediate v into d_name;
dbms_output.put_line('Dname = '|| d_name);
v := 'select loc from dept where dname = :dn';
execute immediate v into lc using d_name;
dbms_output.put_line('Loc = ' || lc);
end;
Bind variables
Declare
V number := 500;
Begin
Update student set marks = v where; -- here v is bind variable
End;
Variable Names
Declare
Marks number(3) := 100;
Begin
Delete student where marks = marks; -- this will delete all the rows in the student table
End;
This can be avoided by using the labeled blocks.
<<my_block>>
Declare
Marks number(3) := 100;
Begin
Delete student where marks = my_block.marks; -- delete rows which has a marks of 100
End;
Getting data into pl/sql variables
Declare
V1 number;
V2 varchar(2);
Begin
Select no,name into v1,v2 from student where marks = 100;
End;
DML and Records
create or replace procedure p(srow in student%rowtype) is
begin
insert into student values srow;
end p;
declare
s student%rowtype;
begin
s.no := 11;
s.name := 'aa';
s.marks := 100;
p(s);
end;
Record based inserts
declare
srow student%rowtype;
begin
srow.no := 7;
srow.name := 'cc';
srow.marks := 500;
insert into student values srow;
end;
Record based updates
declare
srow student%rowtype;
begin
srow.no := 6;
srow.name := 'cc';
srow.marks := 500;
update student set row=srow where no = srow.no;
end;
Using records with returning clause
declare
srow student%rowtype;
sreturn student%rowtype;
begin
srow.no := 8;
srow.name := 'dd';
srow.marks := 500;
insert into student values srow returning no,name,marks into sreturn;
dbms_output.put_line('No = ' || sreturn.no);
dbms_output.put_line('No = ' || sreturn.name);
dbms_output.put_line('No = ' || sreturn.marks);
end;
Forall with non-sequential arrays
declare
type t is table of student.no%type index by binary_integer;
ibt t;
begin
ibt(1) := 1;
ibt(10) := 2;
forall i in ibt.first..ibt.last
update student set marks = 900 where no = ibt(i);
end;
The above program will give error like ‘element at index [2] does not exists.
Usage of indices of to avoid the above error
declare
type t is table of student.no%type index by binary_integer;
ibt t;
type t1 is table of boolean index by binary_integer;
ibt1 t1;
begin
ibt(1) := 1;
ibt(10) := 2;
ibt(100) := 3;
ibt1(1) := true;
ibt1(10) := true;
ibt1(100) := true;
forall i in indices of ibt1
update student set marks = 900 where no = ibt(i);
end;
declare
type t is table of student.no%type index by binary_integer;
ibt t;
type t1 is table of pls_integer index by binary_integer;
ibt1 t1;
begin
ibt(1) := 1;
ibt(10) := 2;
ibt(100) := 3;
ibt1(11) := 1;
ibt1(15) := 10;
ibt1(18) := 100;
forall i in values of ibt1
update student set marks = 567 where no = ibt(i);
end;
Bulk Binds
Ø Passing the entire pl/sql table to the SQL engine in one step is known as bulk bind.
Ø Bulk binds are done using the forall statement.
Ø If there is an error processing one of the rows in bulk DML operation, only that row is rolled back.
Returning clause
Ø This will be used only with DML statements to return data into pl/sql variables.
Ø This will be useful in situations like , when performing insert or update or delete if you want to know the data of the table which has been effected by the DML.
Ø With out going for another SELECT using RETURNING clause we will get the data which will avoid a call to RDBMS kernel.
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