Oracle PL/SQL SELECT INTO statement

Oracle PL/SQL SELECT INTO


SELECT INTO is a key statement in PL/SQL. Data manipulation in PL/SQL typically needs data access to tables and SELECT INTO is the key statement which helps the developers to read the data from data base tables. This is similar to SELECT statement in SQL with a little difference that you need to give a variable list in addition to the selected column list.


Below is the syntax and simple example of PL/SQL.


Syntax
 SELECT column1, column2, ... 
   INTO variable1, variable2, ... 
  WHERE <CONDITION>;
Example
DECLARE
 v_dept_no number;
 v_dept_name varchar2(50);
BEGIN

 SELECT Dept_No, Dept_Name
 INTO v_dept_no, v_dept_name
 From Departments
 Where Dept_No = 10001;

 DBMS_OUTPUT.PUT_LINE(´Department Name :´ || v_dept_name;

END;
/


Please note we need to make sure that the SELECT INTO should returns only one row. In other words, we can say that SELECT INTO must be a single row SELECT. It is important that the data type & width of the variables should match with the data type of columns. When the width of variable is less than the width of the matching column, there is a possibility of overflow error especially when the data length exceeds length of the variable. To avoid these scenarios (data type mismatch and overflows), We can use %TYPE phrase while declaring a variable in place of data type which would help us. For reference, I have written the above example using %TYPE.


DECLARE
 v_dept_no Departments.Dept_No%TYPE;
 v_dept_name Departments.Dept_Name%TYPE;
BEGIN

 SELECT Dept_No, Dept_Name
 INTO v_dept_no, v_dept_name
 FROM Departments
 WHERE Dept_No = 10001;

 DBMS_OUTPUT.PUT_LINE(´Department Name :´ || v_dept_name;

END;
/



Using ROWTYPE

Another best way is using %ROWTYPE. ¨%ROWTYPE¨ is similar to ¨%TYPE¨. But, this phrase defines a variable which can hold the entire row having multiple columns (all the columns in a table) with single variable. We can imagine this as a row in table. Again I am putting above example using ROWTYPE here.

DECLARE
 v_dept_row Departments%ROWTYPE;
BEGIN

 SELECT * INTO v_dept_row
 FROM Departments
 WHERE Dept_No = 10001;

 DBMS_OUTPUT.PUT_LINE(´Department Name :´ || v_dept_row.dept_name;

END;
/

However, the SELECT column list should be of the same order as the column order of the table. Thats why I had given ¨SELECT *¨ here. If the SELECT is not on top of the same table used in ROWTYPE, we need to make sure the column order.

Defining Custom Row Types (RECORD)

We can also a define a custom TYPE which has a set of columns defined by us. And then use our custom TYPE as an data type while declaring. Below is the simple example with syntax.

SYNTAX
TYPE type_name IS RECORD
(
 column1 data_type1,
 column2 data_type2,
 .......
 .......
 .......
);

Example:
DECLARE
 TYPE my_dept_row IS RECORD
 (
       dept_no Departments.Dept_No%Type;
       dept_name Departments.Dept_Name%Type;
 );
 v_dept_row my_dept_row;
BEGIN

 SELECT Dept_No, Dept_Name INTO v_dept_row
   FROM Departments
  WHERE Dept_No = 10001;

 DBMS_OUTPUT.PUT_LINE(´Department Name :´ || v_dept_row.dept_name;

END;
/

I think these PL/SQL sample code would give pretty much good view to any one who is new to the world of PL/SQL. Please feel free to post your valuable comments and feed back.

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Comments 1 comment

Cyrille MODIANO profile image

Cyrille MODIANO 2 years ago from Montreal

Good hub, next step is using BULK COLLECT INTO and FORALL to process many rows at a time

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