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I got a massive satisfaction last week when I was able to bring down the execution time of a sql stored procedure from > 3 hours to mere 2 minutes. It all boiled down to a missing joining key that led to a cartesian product within the tables. Here is how the basic structure of the query (there were plenty of joining columns, however for our convenience lets consider 2 columns only) looked like Select * from                      table1 t1 left join table2 t2 on t1.k1 =t2,k1 and t1.k2 = t2.k2                      left join table3 t3 on t1.k1 = t3.k1 and t1.k2 = t2.k2                      left join table4 t4 on t1.k1 = t4.k1 And this query ran forever when given a particular set of parameters. I started with the approach of joining the parent table with each subsequent table until I met the road block. For example:- Step1 Select * from                      table1 t1 left join table2 t2 on t1.k1 =t2,k1 and t1.k2 = t2.k2 was returning rows Step 2  Select * from