In addition to SHOW INTERNAL TABLES, you can also use the rw_internal_tables table to display internal table information. This is useful when you need to join internal table information with other data.

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Syntax

SHOW INTERNAL TABLES [ FROM schema_name ] [ LIKE_expression ];

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Parameters

ParameterDescription
schema_nameThe schema in which tables will be listed. If not given, tables from the default schema, public, will be listed.
LIKE_expressionFilters the output based on names by applying pattern matching. See details in LIKE pattern matching expressions.

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Example

SHOW INTERNAL TABLES;
                   Name
------------------------------------------
 __internal_v_20_hashjoinright_1019
 __internal_v_20_hashjoindegreeleft_1018
 __internal_v_18_grouptopnnode_1011
 __internal_v_20_hashjoindegreeright_1020
 __internal_v_17_topnnode_1010
 __internal_v_19_hashjoindegreeleft_1014
 __internal_v_20_hashjoinleft_1017
 __internal_v_18_hashaggresult_1012
 __internal_v_19_hashjoinright_1015
 __internal_v_19_hashjoindegreeright_1016
 __internal_v_19_hashjoinleft_1013
(11 rows)
You can view the data in an internal table: 
SELECT * FROM __internal_v_19_hashjoinleft_1013 LIMIT 5;

 orders.o_orderkey | orders.o_orderdate | orders.o_shippriority | customer.c_custkey | orders.o_custkey
-------------------+--------------------+-----------------------+--------------------+------------------
                69 | 1994-06-04         |                     0 |                 85 |               85
               256 | 1993-10-19         |                     0 |                125 |              125
              1154 | 1992-02-15         |                     0 |                 37 |               37
              1792 | 1993-11-09         |                     0 |                 49 |               49
              1894 | 1992-03-30         |                     0 |                 76 |               76
(5 rows)