All column width

Question

i want to knwo the total width of all the columns in a single table
e.g 1st column is char(5) data_length column in user_tab_columns will show 5 byets
2nd column is varchar(5) data_length column in user_tab_columns will show 5 byets
3rd column is number(3) data_length column in user_tab_columns will show 22 byets
4th column is date data_length column in user_tab_columns will show 7 byets
means total width of all 4 columns is 5+5+22+7=39 byte but i want total in characters
so for now i'll elimanate date columns and will count total no of character in two group 1st is char and varchar from data_length column and 2nd is for number count from data_precision column
so the query is like this
select table_name,sum(data_length) as length from user_tab_columns where data_type IN ('CHAR','VARCHAR2') GROUP BY TABLE_NAME
union
select table_name,sum(data_precision) as length from user_tab_columns where data_type='NUMBER' group by table_name
this will give
TABL LENGTH
EXM 3
EXM 10
how do i get total of this 10+3 in sql query

Answer 1

Use DECODE.
SELECT   table_name,
         SUM (DECODE (data_type,
                      'CHAR', data_length,
                      'VARCHAR2', data_length,
                      'NUMBER', data_precision
             ) AS LENGTH
    FROM user_tab_columns
   WHERE data_type IN ('CHAR', 'VARCHAR2', 'NUMBER')
GROUP BY table_nameBut these queries may not give you the correct result. DATA_PRECISION is not always filled for NUMBER columns. For example if you have a NUMBER column added without a precision and scale it is shown as below in user_tab_columns.
SQL> create table t(col1 number);
Table created.
SQL> select column_name,data_type,data_length,data_precision
  2  from user_tab_columns
  3  where table_name='T'
  4  ;
COLUMN_NAME                    DATA_TYPE  DATA_LENGTH DATA_PRECISION
COL1                           NUMBER              22Message was edited by:
Yas
Message was edited by:
Yas