Hadoop Pig学习笔记(一) 各种SQL在PIG中实现
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 zhangsan 23 1 lisi 24 1 wangmazi 30 1 meinv 18 0 dama 55 0 zhangsan231 lisi241 wangmazi301 meinv180 dama550 tmp_file_2: Txt代码 1 a 23 bb 50 ccc 30 dddd 66 eeeee 1a 23bb 50ccc 30dddd 66eeeee 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; 本文作者：佚名 来源：51CTO
