各种SQL在PIG中实现

{% include JB/setup %}

我这里以Mysql 5.1.x为例,Pig的版本是0.8 同时我将数据放在了两个文件,存放在/tmp/data_file_1和/tmp/data_file_2中.文件内容如下:
tmp_file_1:

Txt代码  收藏代码
zhangsan    23  1  
lisi    24  1  
wangmazi    30  1  
meinv   18  0  
dama    55  0  

tmp_file_2:

Txt代码  收藏代码
1   a  
23  bb  
50  ccc  
30  dddd  
66  eeeee  

1.从文件导入数据

      1)Mysql (Mysql需要先创建表).
         CREATE TABLE TMP_TABLE(USER VARCHAR(32),AGE INT,IS_MALE BOOLEAN);
         CREATE TABLE TMP_TABLE_2(AGE INT,OPTIONS VARCHAR(50));   -- 用于Join
         LOAD DATA LOCAL INFILE '/tmp/data_file_1'  INTO TABLE TMP_TABLE ;
         LOAD DATA LOCAL INFILE '/tmp/data_file_2'  INTO TABLE TMP_TABLE_2;
      2)Pig
          tmp_table = LOAD '/tmp/data_file_1' USING PigStorage('\t') AS (user:chararray, age:int,is_male:int);
          tmp_table_2= LOAD '/tmp/data_file_2' USING PigStorage('\t') AS (age:int,options:chararray);

2.查询整张表

     1)Mysql
        SELECT * FROM TMP_TABLE;
     2)Pig
        DUMP tmp_table;

3.查询前50行

     1)Mysql
        SELECT * FROM TMP_TABLE LIMIT 50;
     2)Pig
         tmp_table_limit = LIMIT tmp_table 50;
         DUMP tmp_table_limit; 

4.查询某些列

    1)Mysql
        SELECT USER FROM TMP_TABLE;
    2)Pig
        tmp_table_user = FOREACH tmp_table GENERATE user;
        DUMP tmp_table_user;

5.给列取别名

    1)Mysql
       SELECT USER AS USER_NAME,AGE AS USER_AGE FROM TMP_TABLE;
    2)Pig
       tmp_table_column_alias = FOREACH tmp_table GENERATE user AS user_name,age AS user_age;
       DUMP tmp_table_column_alias; 

6.排序

    1)Mysql
       SELECT * FROM TMP_TABLE ORDER BY AGE;
    2)Pig
        tmp_table_order = ORDER tmp_table BY age ASC;
        DUMP tmp_table_order;

7.条件查询

    1）Mysql
        SELECT * FROM TMP_TABLE WHERE AGE>20;
    2) Pig
        tmp_table_where = FILTER tmp_table by age > 20;
        DUMP tmp_table_where;

8.内连接Inner Join

    1)Mysql
       SELECT * FROM TMP_TABLE A JOIN TMP_TABLE_2 B ON A.AGE=B.AGE;
    2)Pig
        tmp_table_inner_join = JOIN tmp_table BY age,tmp_table_2 BY age;
        DUMP tmp_table_inner_join;

9.左连接Left Join

   1)Mysql
       SELECT * FROM TMP_TABLE A LEFT JOIN TMP_TABLE_2 B ON A.AGE=B.AGE;
   2)Pig
      tmp_table_left_join = JOIN tmp_table BY age LEFT OUTER,tmp_table_2 BY age;
      DUMP tmp_table_left_join;

10.右连接Right Join

     1)Mysql
        SELECT * FROM TMP_TABLE A RIGHT JOIN TMP_TABLE_2 B ON A.AGE=B.AGE;
     2)Pig
        tmp_table_right_join = JOIN tmp_table BY age RIGHT OUTER,tmp_table_2 BY age;
        DUMP tmp_table_right_join;

11.全连接Full Join

     1)Mysql
        SELECT * FROM TMP_TABLE A  JOIN TMP_TABLE_2 B ON A.AGE=B.AGE
            UNION SELECT * FROM TMP_TABLE A LEFT JOIN TMP_TABLE_2 B ON A.AGE=B.AGE
            UNION SELECT * FROM TMP_TABLE A RIGHT JOIN TMP_TABLE_2 B ON A.AGE=B.AGE;

     2)Pig
        tmp_table_full_join = JOIN tmp_table BY age FULL OUTER,tmp_table_2 BY age;
        DUMP tmp_table_full_join;

12.同时对多张表交叉查询

      1)Mysql
         SELECT * FROM TMP_TABLE,TMP_TABLE_2;
      2)Pig
         tmp_table_cross = CROSS tmp_table,tmp_table_2;
         DUMP tmp_table_cross;

13.分组GROUP BY

     1)Mysql
        SELECT * FROM TMP_TABLE GROUP BY IS_MALE;
     2)Pig
        tmp_table_group = GROUP tmp_table BY is_male;
        DUMP tmp_table_group;

14.分组并统计

       1)Mysql
         SELECT IS_MALE,COUNT(*) FROM TMP_TABLE GROUP BY IS_MALE;
       2)Pig
          tmp_table_group_count = GROUP tmp_table BY is_male;
          tmp_table_group_count = FOREACH tmp_table_group_count GENERATE group,COUNT($1);
          DUMP tmp_table_group_count;

15.查询去重DISTINCT

       1)MYSQL
          SELECT DISTINCT IS_MALE FROM TMP_TABLE;
       2)Pig
          tmp_table_distinct = FOREACH tmp_table GENERATE is_male;
          tmp_table_distinct = DISTINCT tmp_table_distinct;
          DUMP  tmp_table_distinct;