Find most used data type in IBM Db2 database

Query below returns data types used in a database ordered by the number of their occurance.

Query

select col.typename as data_type,
       count(*) as columns,
       cast(100.0 *
               count(*) / 
                   (select count(*) from syscat.tables tab
                    inner join syscat.columns col 
                    on col.tabschema = tab.tabschema
                    and col.tabname = tab.tabname
                    where tab.type = 'T'
                    and tab.tabschema not like 'SYS%') 
       as decimal (14,2))  as percent_columns, 
       count(distinct tab.tabschema concat '.' concat tab.tabname) as tables,
       cast(100.0 * 
           count(distinct tab.tabschema concat '.' concat tab.tabname) / 
                (select count(*) from syscat.tables 
                where type = 'T' and tabschema not like 'SYS%')
       as decimal (14,2)) as percent_tables
 from syscat.tables tab
    inner join syscat.columns col 
    on col.tabschema = tab.tabschema and col.tabname = tab.tabname
where tab.type = 'T'
    and tab.tabschema not like 'SYS%'
group by col.typename
order by count(*) desc

Columns

  • data_type - built in or user data type without length or precision, e.g. int, varchar or date
  • columns - number of columns in a database with this data type
  • percent_columns - percentage of columns with this data type. Rows add up to 100%
  • tables - number of tables in a database with this data type
  • percent_tables - percentage of tables with columns with this data type.

Rows

  • One row represents one data type
  • Scope of rows: all data types used in a database
  • Ordered by number of columns descending

Sample results

Those results show data types used in GSDB database. As you can see most popular data type is VARCHAR - it is used in 2006 columns which is 75.36% of all columns in 106 tables (which 70.19% of all tables).

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