ORA-01789: query block has incorrect number of result columns

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ORA-01789: query block has incorrect number of result columns

You may see this error in the following situation:

create table test1_1789 (
col_a varchar2(30),
col_b number,
col_c date);

create table test2_1789 (
col_a varchar2(30),
col_c number,
col_b date,
col_d char(1));

select * from test1_1789
union all
select * from test2_1789;

ORA-01789: query block has incorrect number of result columns

Table test2_1789 contains one column too many.

This fact becomes a problem because we are using * as column list specifier and it can be avoided by specifying an explicit list of columns common to both tables.


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