diff options
Diffstat (limited to 'sql/table.h')
-rw-r--r-- | sql/table.h | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/sql/table.h b/sql/table.h index f3a7f278604..14ab0027a79 100644 --- a/sql/table.h +++ b/sql/table.h @@ -1281,9 +1281,16 @@ public: /* number of select if it is derived table */ uint derived_select_number; /* - 0 or JOIN_TYPE_{LEFT|RIGHT}. Currently this is only compared to 0. - If maybe_null !=0, this table is inner w.r.t. some outer join operation, - and null_row may be true. + Possible values: + - 0 by default + - JOIN_TYPE_{LEFT|RIGHT} if the table is inner w.r.t an outer join + operation + - 1 if the SELECT has mixed_implicit_grouping=1. example: + select max(col1), col2 from t1. In this case, the query produces + one row with all columns having NULL values. + + Interpetation: If maybe_null!=0, all fields of the table are considered + NULLable (and have NULL values when null_row=true) */ uint maybe_null; int current_lock; /* Type of lock on table */ |