Nested table in oracle

 The syntax for creating a nested table 

CREATE TYPE a_simple_udt_t IS TABLE OF NUMBER(10);

SQL> CREATE TABLE a_table (
  2    col1 number,
  3    col2 a_simple_udt_t )
  4  NESTED TABLE col2 STORE AS a_table_col2;
The NESTED TABLE clause specifies the name of the table used to store the data in the nested column.