Find most used data type in MySQL database

The query below returns data types used in a database (schema) ordered by the number of their occurrence.


select data_type,
       count(*) as columns,
       cast(100*count(*)/sum_all.columns as decimal(36,2)) 
            as percent_columns,
       count(distinct concat(col.table_schema, '.', col.table_name))
            as tables,
       cast(100*count(distinct concat(col.table_schema,'.',col.table_name)) 
            / sum_all.tables as decimal(36,2)) as percent_tables
from information_schema.columns col
join (select count(distinct concat(c.table_schema, '.', c.table_name))
                    as tables,
             count(*) as columns
      from information_schema.columns c
      join information_schema.tables t
           on c.table_schema = t.table_schema
           and c.table_name = t.table_name
      where t.table_schema not in ('information_schema', 'mysql',
                                   'performance_schema', 'sys')
            and t.table_type = 'BASE TABLE'
      ) sum_all on true
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', 'mysql',
                               'performance_schema', 'sys')
      and tab.table_type = 'BASE TABLE'
group by data_type,
order by columns desc;


  • data_type - built-in or user data type without length or precision, e.g. int, varchar or datetime
  • columns - number of columns in a database (schema) with this data type
  • percent_columns - percentage of columns with this data type. The rows total 100%
  • tables - number of tables in a database (schema) with this data type
  • percent_tables - percentage of tables with columns that have this data type.


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

Sample results

Sample results for the Sakila database (schema). As you can see most popular data type is smallint and varchar - both are used in 20 columns which is 22.5% of all columns in 16 tables.

Note that smallint data type is used in 14 tables that represent 87.5% of all tables, whereas varchar data type is used in 9 tables which is 56.3%.

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