Avoid parameter sniffing for exists subquery, fix tests

Author: yoosoopov

QueryBuilder.Tests/SqlServer/NestedSelectTests.cs

@@ -56,7 +56,7 @@ public void SqlCompile_QueryLimitAndNestedLimit_BindingValue()
             // var q = new Query().From("Foo").Where("C", "c").WhereExists(n).Where("A", "a");
 
             var actual = compiler.Compile(q).ToString();
-            Assert.Contains("SELECT * FROM [Foo] WHERE [x] = true AND NOT EXISTS (SELECT TOP (1) 1 FROM [Bar])",
+            Assert.Contains("SELECT * FROM [Foo] WHERE [x] = true AND NOT EXISTS (SELECT 1 FROM [Bar])",
                 actual);
             // Assert.Contains("SELECT * FROM [Foo] WHERE [C] = 'c' AND EXISTS (SELECT TOP (1) 1 FROM [Bar]) AND [A] = 'a'", actual);
         }