MySQL 8.0

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create table example_table(
  pk int auto_increment primary key
, textfield char(1)
, do_not_touch boolean
)
EXPLAIN format=tree
UPDATE example_table
SET textfield = 'X'
WHERE textfield = 'Y'
and pk not in (SELECT pk FROM (SELECT pk FROM example_table WHERE do_not_touch =1)as t) ;


EXPLAIN


-> Update example_table (immediate)
    -> Nested loop antijoin
        -> Filter: (example_table.textfield = 'Y')  (cost=0.35 rows=1)
            -> Table scan on example_table  (cost=0.35 rows=1)
        -> Index lookup on t using <auto_key0> (pk=example_table.pk)
            -> Materialize
                -> Filter: (example_table.do_not_touch = 1)  (cost=0.35 rows=1)
                    -> Table scan on example_table  (cost=0.35 rows=1)



EXPLAIN
UPDATE example_table
SET textfield = 'X'
WHERE textfield = 'Y'
and do_not_touch !=1


id
select_type
table
partitions
type
possible_keys
key
key_len
ref
rows
filtered
Extra


1
UPDATE
example_table
null
index
null
PRIMARY
4
null
1
100.00
Using where