各种SQL在Pig中实现

 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:

zhangsan    231
lisi    241
wangmazi    301
meinv   180
dama    550

tmp_file_2:

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;

本文源自：http://guoyunsky.iteye.com/blog/1317084