added test case for limit offset

Author: florianlechner

select_test.go

@@ -91,3 +91,65 @@ func ExampleSelectBuilder_join() {
 	// SELECT u.id, u.name, c.type, p.nickname FROM user u JOIN contract c ON u.id = c.user_id AND c.status IN (?, ?, ?) RIGHT OUTER JOIN person p ON u.id = p.user_id AND p.surname LIKE ? WHERE u.modified_at > u.created_at + ?
 	// [1 2 5 %Du 86400]
 }
+
+func ExampleSelectBuilder_limit_offset() {
+
+	sb := NewSelectBuilder()
+	sb.Select("*")
+	sb.From("user")
+
+	// first test case: limit and offset < 0
+	// will not add LIMIT and OFFSET to either query for MySQL or PostgresSQL
+	sb.Limit(-1)
+	sb.Offset(-1)
+
+	pgSQL, _ := sb.BuildWithFlavor(PostgreSQL)
+	fmt.Println(pgSQL)
+
+	mySQL, _ := sb.BuildWithFlavor(MySQL)
+	fmt.Println(mySQL)
+
+	// second test case: limit <= 0 and offset >= 0
+	// doesn't add offset for MySQL as limit <= 0
+	// just adds offset to PostgresSQL with no limit as it is not specified
+	sb.Limit(-1)
+	sb.Offset(0)
+
+	pgSQL, _ = sb.BuildWithFlavor(PostgreSQL)
+	fmt.Println(pgSQL)
+
+	mySQL, _ = sb.BuildWithFlavor(MySQL)
+	fmt.Println(mySQL)
+
+	// third test case: limit >= 0 and offset >= 0
+	// adds offset and limit for MySQL and PostgresSQL, the query will not return a row (hint: can be used to check if table exists)
+	sb.Limit(0)
+	sb.Offset(0)
+
+	pgSQL, _ = sb.BuildWithFlavor(PostgreSQL)
+	fmt.Println(pgSQL)
+
+	mySQL, _ = sb.BuildWithFlavor(MySQL)
+	fmt.Println(mySQL)
+
+	// forth test case: limit >= 0 and offset <= 0
+	// adds limit for MySQL and PostgresSQL and omits offset
+	sb.Limit(0)
+	sb.Offset(-1)
+
+	pgSQL, _ = sb.BuildWithFlavor(PostgreSQL)
+	fmt.Println(pgSQL)
+
+	mySQL, _ = sb.BuildWithFlavor(MySQL)
+	fmt.Println(mySQL)
+
+	// Output:
+	// SELECT * FROM user
+	// SELECT * FROM user
+	// SELECT * FROM user OFFSET 0
+	// SELECT * FROM user
+	// SELECT * FROM user LIMIT 0 OFFSET 0
+	// SELECT * FROM user LIMIT 0 OFFSET 0
+	// SELECT * FROM user LIMIT 0
+	// SELECT * FROM user LIMIT 0
+}