当使用小写的表名时，DatabaseMetaData.getColumns（）返回空的ResultSet，但是在上层使用右侧的ResultSet

Question

I use oracle 11g,and create a table like this:

create table test1(
id int,
name varchar(10),
inserttime date
)

Then I use the jdbc method

DatabaseMetaData.getColumns(null, null, "test1", null)

and get empty ResultSet. but when I use

DatabaseMetaData.getColumns(null, null, "TEST1", null)

I can get the right ResultSet.

Why?

Answer 1

This is because internally, OracleDatabaseMetaData.getColumns() executes a query against the all_tab_columns data dictionary view, where it matches the table name pattern against all_tab_columns.table_name .

By convention, Oracle stores identifiers (such as the table name here) in data dictionaries in uppercase format. You can verify this by executing the following query in the db:

SELECT * FROM all_tab_columns t where t.table_name = 'TEST1';

The case-sensitivity of the table identifier here is indeed counter-intuitive, especially because table identifiers are case-insensitive in Oracle SQL.