Find most used data type in Redshift

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

Query

with stats as (
    select count(distinct col.table_schema||'.'||col.table_name) 
            as sum_tables,
           count(col.column_name) as sum_columns
    from information_schema.columns col
    join information_schema.tables tab
         on col.table_schema = tab.table_schema
         and col.table_name = tab.table_name
    where tab.table_schema not in ('information_schema', 'pg_catalog')
          and tab.table_type = 'BASE TABLE'
)
select col.udt_name as typname,
       count(distinct col.table_schema||'.'||col.table_name) as tables,
       round(100.0*
             count(distinct col.table_schema||'.'||col.table_name)
             / (select sum_tables from stats)
             , 2) as percent_tables,
       count(col.column_name) as columns,
       round(100.0*count(col.column_name)
             / (select sum_columns from stats)
             , 2) as percent_column
from information_schema.columns col
join information_schema.tables tab
     on col.table_schema = tab.table_schema
     and col.table_name = tab.table_name
where tab.table_schema not in ('information_schema', 'pg_catalog')
      and tab.table_type = 'BASE TABLE'
group by col.udt_name
order by columns desc,
         tables desc;

Columns

  • typname - built in or user data type without length or precision, e.g. int, varchar or date
  • tables - number of tables in a database with this data type
  • percent_tables - percentage of tables with columns with this data type.
  • 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%.

Rows

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

Sample results

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