SQL開發例項和優化

找出連續的資料 如1,2,3,48,50,51,52,53,67,68
找出連續的數字的起點和重點
1,3
48,48
51,53
67,68
create table test.range_problem(
 
    a int not null,
    primary key (a));
insert into test.range_problem values(1);
 
insert into test.range_problem values(2);

insert into test.range_problem values(3);

insert into test.range_problem values(48);

insert into test.range_problem values(50);

insert into test.range_problem values(51);

insert into test.range_problem values(52);

insert into test.range_problem values(53);

insert into test.range_problem values(66);

 insert into test.range_problem values(67);
 
 
  
  
   --思路1 找最後一個不連續的數
   SELECT T1.A
   FROM test.range_problem T1
   WHERE NOT EXISTS
   (
     SELECT A
     FROM test.range_problem T2
     WHERE T2.A -1 = T1.A
   )
  
  
   --思路2  找所有行對應的結束值
   SELECT ROW_NUMBER()OVER(ORDER BY TBASE.A) ID
         ,TBASE.A
         ,(SELECT Min(A)
           FROM test.range_problem T1
           WHERE NOT EXISTS
           (
             SELECT A
             FROM test.range_problem T2
             WHERE T2.A -1 = T1.A
           )
           AND T1.A >= TBASE.A  --T1.A 是3,48,53,67 TBASE.A 是每行的值
          ) A_END
                         
   FROM test.range_problem TBASE
  
   --思路3 分組後找出所有連續的起始值和結束值
   SELECT MIN(A) A_START, A_END
     FROM(
     SELECT ROW_NUMBER()OVER(ORDER BY TBASE.A) ID
           ,TBASE.A
           ,(SELECT Min(A)
             FROM test.range_problem T1
             WHERE NOT EXISTS
             (
               SELECT A
               FROM test.range_problem T2
               WHERE T2.A -1 = T1.A
             )
             AND T1.A >= TBASE.A  --T1.A 是3,48,53,67 TBASE.A 是每行的值
            ) A_END
                           
     FROM test.range_problem TBASE
   ) T
   GROUP BY T.A_END
  
   --對上面語句的優化
   WITH POT AS(
           SELECT A
           FROM test.range_problem T
           WHERE NOT EXISTS
           ( SELECT A
             FROM test.range_problem TC
             WHERE TC.A -1 = T.A)
         )
       
        
         SELECT TBASE.A A_START,(SELECT MIN(A)
                               FROM  POT T
                               WHERE TBASE.A <= T.A 
                               ) A_END
         FROM test.range_problem TBASE

          

 

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