MySQL infinite loop in a subquery? -


the following query results infinite loop:

select      *,     (select              t2.`value`                     `table` t2                     t2.`variable` = 'xxx'                 , t2.`read` = (select                      max(t1.`read`)                                     `table` t1                                     t1.`variable` = 'xxx'                         , unix_timestamp(t1.`read`) < (1401801648 - n.integers)                 )     )     (select          @n:=@n + 1 integers             mysql.help_relation, (select @n:=0) dum     limit 48) n

i need result 48 rows 48 different time ranges (in example 1401801648 minus {1..48}). each row should contain value depending on current time range. query on bottom these 48 ranges. query in middle needed find date newest entry older calculated timestamp (1401801648 - n.integers). upper query tells me value of row date query in middle.

when "n.integers" replaced number works fine.

without subquery (t2) query not in loop(?):

select      *,     (select              max(t1.`read`)                     `table` t1                     t1.`variable` = 'xxx'                 , unix_timestamp(t1.`read`) < (1401801648 - n.integers)     )     (select          @n:=@n + 1 integers             mysql.help_relation, (select @n:=0) dum     limit 48) n

an alternative method avoiding using variables:-

select sub1.a_cnt, t2.value table t2 inner join (     select sub1.a_timestamp, sub1.a_cnt, t1.variable, max(t1.read) max_timestamp         (         select (1401801648 - units.i + 10 * tens.i) a_cnt,(1401801648 - units.i + 10 * tens.i) a_timestamp                 (select 0 union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) units,         (select 0 union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) tens         units.i + 10 * tens.i between 1 , 48     ) sub1     inner join table t1     , unix_timestamp(t1.read) < sub1.a_timestamp     t1.variable = 'xxx'     group sub1.a_timestamp ) sub2 on t2.read = sub2.max_timestamp , t2.variable = sub2.variable

this uses load of unioned queries getting constants generate numbers 0 9, cross joins against copy of , minor calulation numbers 0 99, clause narrow down range 1 48, , uses calculate timestamps required.

this joined against table max read date each timestamp / generated number.

the results of joined against table other details row (in case value column).

not tested gives idea.


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