并行处理： 可以在很多语句中指定reducer的数量 group, join, cogroup, cross, distinct, order (复习：reduce的任务个数设置为稍小于集群中的reduce任务槽数) 参数替换：在pig语句中使用$加变量名的方式使用外部定义的变量值，在运行时可以通过"-param input=”设置变量的值， 或者通过"-param_file ”来指定参数文件。 动态参数：很多Unix shell用反引号引用的命令来替换实际值，如`date “+%Y-%m-%d” `会按规定格式输出日期。 这个可以放在-param或参数文件中来动态得到一个值。 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 tmp_file_2: Txt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 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; 更多精彩内容请关注：http://bbs.superwu.cn 关注超人学院微信二维码： |
原文地址：http://blog.csdn.net/crxy2014/article/details/46009883
