tsql - Code is executed although condition is false -

i have view v. selecting data view takes ten seconds execute because of referencing many many other views , tables. there's no way change this.

furthermore, there changelog table ( cl ) holds information whether datasets of v ( , / or other tables / views have reloaded, e.g.:

id, refid, table 1, 1, v 2, 2, v 3, 3, 4, 1, b 

id pk, auto-increment. refid refers id-column of each referring table / view. table holds name of referring table / view

now, there query checks if there datasets in cl referring view v.

q1:

select    v.*    cl inner join v    on v."id" = cl."refid"   , cl."table" = 'v' 

in above example, 2 records cl affected ( id 1 , 2 ).

if no record affected @ ( no record "table" = 'v' in cl ) expect instant result of 0 executing second query q1 ( thought optimizer determine join-condition returns 0 results in cl , therefore there no need execute select on view v bottleneck, does. )

what have tried after this:

a) moving part of join-condition ( cl."table" = 'v' ) where clause.

b) removing join , rewrite

if (( select count(1) cl "table" = 'v' ) > 0 ) begin   <do references bottleneck-view v> end 

if if-condition returns false, hoped code between begin , end not executed. is. runtime of query in b) same select * v, if there's no record table ='v' in cl).

what doing wrong?