本文主要是介绍sql与pig比较，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
sql与pig比较1 .select select column_name from table_name; foreach alians generate column_name;
2. select * select * from table_name; foreach alias generate *;
3 .distinct select distinct column_name from table_name; distinct(foreach alians generate column_name,cloumn_name);
4 .where select colum_name ,column_name from table_name where column_name opertor value foreach(filter alias by column_name operator value) generate colum_name,column_name;
5 .and/or ...where(column_name operator value1 and column_name operator value2) or column_name operator value3 filter alias by (column_name operator value1 and column_name operator value2) or column_name operator value3;
6 order by ...order by colum_name asc|desc,column_name asc|desc; order alias by colum_name asc|desc,column_name asc|desc;
7. top/limit select top number colum_name from table_name order by column_name asc|desc foreach (group alias by column_name) generate limit alias number
8 group by select function(column_name) from table group by column_name foreach(group alias by column_name) generate function(alias.column_name)
9 like where column_name like pattern; filter alias by regeex_extract(column_name,pattern,1) is not null;
10 . in where column_name in(value1,value2,...); filter alias by column_name in(value1,value2,...)
11 .join select column_name(s) from table1 join table2 on table1.column_name=table2.column_name; foreach (join alias1 by column_name,alias2 by column_name) generate column_name(s);
sql function
1 .left/right/full outer join select column_name(s) from table1 left|rigth|full outer join table2 on table1.cloumn_name=table2.cloumn_name; foreach (join alias1 by column_name left|rigth|full,alias2 by column_name) generate column_name(s)
2 .union all select column_name(s) from table1 union all select column_name(s) from table2; union alias1,alias2
3. avg select avg(column_name) from table_name; foreach(group alias all) generate avg(alias.column_name);
4. count select count(cloumn_name) from table_name; foreach(group alias all) generate avg(alias);
5.count distinct select count(distinct column_name) from table_name; foreach alias{unique_column=distinct column_name;generate count(unique_column)};
6. max select max(column_name) from table_name; foreach(group alias all) generate max(alias.column_name)
7. min select min(column_name) from table_name; foreach(group alias all) generate min(alias.column_name)
8. sum select sum(column_name) from table_name; foreach(group alias all) generate sum(alias.column_name)
9. having ...having aggregate_function(column_name) operate value; filter alias by aggregate_function(column_name) operate value
10. ucase/upper select ucase(column_name) from table_name; foreach alias generate upper(column_name)
11. lcase/lower select lcase(column_name) from table_name; foreach alias generate lower(column_name)
12 .substring select substring(column_name,start,length) as some_name from table_name; foreach alias generate substring(column_name,start,length) as some_name
13.select len(column_name) from table_name; foreach alias generate size(cloumn_name);
14 .round select round(column_name,0) from table ; foreach alias generate round(cloumn_name);
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