Details
Major Description
Note the differences between the 2 select result sets.
create table t10 (a datetime, b int); |
insert into t10 select date_add('2020-01-01', interval seq day), seq from seq_1_to_10; |
insert into t10 values (NULL, NULL); |
create table t20 select * from t10; |
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select * from t10, t20 where t10.a <=> t20.a; |
set join_cache_level=6; |
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select * from t10, t20 where t10.a <=> t20.a; |
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drop table t10, t20; |
The hash join fails where the datetime field contains a null value;