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The following page has been changed by Thatha: http://wiki.apache.org/pig/PigLatin The comment on the change is: Formatting ------------------------------------------------------------------------------ || '''Field referred to by position''' || '''$0''' || Data Atom '1' || '''In Pig, positions start at 0 and not 1''' || || '''Field referred to by name''' || '''f2'''|| Bag {<2,3>,<4,6>,<5,7>} || || || '''Projection''' of another data item || '''f2.$0''' || Bag {<2>,<4>,<5>} - the bag f2 projected to the first field || || - || '''Map Lookup''' against another data item || '''f3#'apache'''' || Data Atom 'search' ||* User's responsibility to ensure that a lookup is written only against a data map, otherwise a runtime error is thrown <br> * If the key being looked up does not exist, a Data Atom with an empty string is returned|| + || '''Map Lookup''' against another data item || '''f3#'apache'''' || Data Atom 'search' ||User's responsibility to ensure that a lookup is written only against a data map, otherwise a runtime error is thrown. If the key being looked up does not exist, a Data Atom with an empty string is returned.|| || '''Function''' applied to another data item || '''SUM(f2.$0)''' || 2+4+5 = 11 || SUM is a builtin Pig function. See PigFunctions for how to write your own functions || || '''Infix Expression''' of other data items || '''COUNT(f2) + f1 / '2.0'''' || 3 + 1 / 2.0 = 3.5 || || || '''Bincond''', i.e., the value of the data item is chosen according to some condition || '''(f1 = = '1' ? '2' : COUNT(f2))''' || '2' since f1=='1' is true. If f1 were != '1', then the value of this data item for t would be COUNT(f2)=3 || See [#Specifying_Conditions Conditions] for what the format of the condition in the bincond can be ||