Get Maximum Length allowed in column | Oracle - sql

Question

How to get the Max and Min length allowed in column of varchar2.
I have to test for incoming data from the temp table which is coming from some remote db. And each row value is to be tested for specific columns that it has maximum or minimum value which can be set into the column.
So I was to get the column specs using its schema details. I did make a proc for that:
PROCEDURE CHK_COL_LEN(VAL IN VARCHAR2,
MAX_LEN IN NUMBER :=4000,
MIN_LEN IN NUMBER :=0,
LEN_OUT OUT VARCHAR2)
IS
BEGIN
IF LENGTH(VAL)<MIN_LEN THEN
LEN_OUT := 'ERROR';
RETURN;
ELSIF LENGTH(VAL)>MAX_LEN THEN
LEN_OUT := 'ERROR';
RETURN;
ELSE
LEN_OUT := 'SUCCESS';
RETURN;
END IF;
END;
END CHK_COL_LEN;
But the problem is, it is not reusable and is a bit hardcoded. I have to explicitly send MAX and MIN value for each value along with the data to be checked.
So at the proc call, it's something like:
CHK_COL_LEN(EMP_CURSOR.EMP_ID, 5, 1, LEN_ERROR_MSG);
I instead want something like: (If something like this exist!)
CHK_COL_LEN(EMP_CURSOR.EMP_ID,
EMP.COLUMN_NAME%MAX_LENGTH,
EMP.COLUMN_NAME%MIN_LENGTH,
LEN_ERROR_MSG)
Thanks in advance.
EDIT
select max(length(col)) from table;
This is a solution, but again I will have to run this query each time to set the two variables for MAX and MIN value. And running extra two queries for each value and then setting 2 variables will cost be significant lose in performance when in have about 32 tables, each with 5-8 varchar2 columns and average rows of about 40k-50k in each table

Answer 1

You can query the table 'user_tab_columns table' to retrieve metadata information of a specific table:
SELECT
COLUMN_NAME, DATA_LENGTH, DATA_PRECISION
FROM
user_tab_columns
WHERE
t.table_name IN ('<YOURTABLE>');
with this information you can query the metadata directly in your stored procedure:
...
SELECT
CHAR_LENGTH INTO max_length
FROM
user_tab_columns
WHERE
table_name = '<YOURTABLE>' AND COLUMN_NAME = '<YOURCOLUMN>';
...
Exmple Procedure to get max length of table/column:
create or replace PROCEDURE GET_MAX_LENGTH_OF_COLUMN(
tableName IN VARCHAR2,
columnName IN VARCHAR2,
MAX_LENGTH OUT VARCHAR2)
IS
BEGIN
SELECT CHAR_LENGTH INTO MAX_LENGTH
FROM user_tab_columns
WHERE table_name = tableName AND COLUMN_NAME = columnName;
END GET_MAX_LENGTH_OF_COLUMN;

Answer 2

Try creating your procedure like this:
create or replace procedure Checking_size(column_name varchar2,columnvalue varchar2,state out varchar2) is
begin
execute immediate 'declare
z '||column_name||'%type;
begin
z:=:param2;
end;' using columnvalue;
state:='OK';
exception when value_error then
state:='NOT OK';
end;
As you can see i simulate an error assignment. If columnvalue length is bigger than the column i pass as column_name it will throws value_error exception and return NOT OK, else return OK.
For example, if your_table.your_column refer to a column with length (3) then return NOT OK.
declare
state varchar2(10);
begin
Checking_size('your_table.your_column','12345',state);
dbms_output.put_line(state);
end;

Answer 3

If the list of tables is not much you can specify the MIN Value using CHECK Constraint on the table.
Any DML on the table would automatically fail if it exceeds length assigned to that column.
CREATE TABLE suppliers
(
supplier_id numeric(4),
supplier_name varchar2(50),
CONSTRAINT check_supplier_id
CHECK (length(supplier_name) > 5 )
);