在Oracle中，是否可以查询具有相同数据类型的列

Question

I have table which has almost hundred fields. I want to get all the fields which data type is date. Is it possible in oracle to write such a query to return fields only contain a certain data type? Here is my pseudo query:

Select * from mytable 
where colum_datatype is date

Similarly, I want to get all fields which is varchar2 type. is it possible to do that? I can find all the date fields manually and put them in the query but I just want to know is there another way to do it. Thank you!

Answer 1

You can query one of the system tables/views to get the list of columns:

select column_name
from all_tab_cols
where owner = :owner and table_name = :table and data_type = 'DATE';

If you need a one-off solution, just aggregate these and plug into a sql query. You can construct the entire SQL query:

select 'SELECT ' || listagg(column_name, ', ') within group (order by column_id) || ' FROM ' || :table
from all_tab_cols
where owner = :owner and table_name = :table and data_type = 'DATE';

You can also put the query into a string and use dynamic SQL ( execute immediate ) to run the query.

Answer 2

Sorry, no such functionality exists in vanilla SQL. You may be able to simulate such functionality by creating a PL/SQL function that returns a cursor to a dynamically created SQL statement.