【转载】各种SQL在PIG中实现

转自：http://guoyunsky.iteye.com/blog/1317084

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:

1. zhangsan    23  1
2. lisi    24  1
3. wangmazi    30  1
4. meinv   18  0
5. dama    55  0

tmp_file_2:

1. 1   a
2. 23  bb
3. 50  ccc
4. 30  dddd
5. 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;