[GitHub] [calcite] weidong3630 edited a comment on issue #1422: [CALCITE-3300] Add a star identifier as operand to "SqlCountAggFunction" if no operands given while in the method "createCall"

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weidong3630 edited a comment on issue #1422: [CALCITE-3300] Add a star identifier as operand to "SqlCountAggFunction" if no operands given while in the method "createCall"
URL: https://github.com/apache/calcite/pull/1422#issuecomment-545300895
 
 
   @jinxing64 Like @julianhyde said,
   Calcite allows multiple arguments to COUNT. It counts a row if none of the arguments are NULL:
   > select count(x, y), count(x), count(y), count(*)
   > from (values (1, 2),
   >    (3, CAST(NULL AS INTEGER))) as t (x, y);
   +-----------------+-----------------+-----------------+-----------------+
   |     EXPR$0      |     EXPR$1      |     EXPR$2      |     EXPR$3      |
   +-----------------+-----------------+-----------------+-----------------+
   | 1               | 2               | 1               | 2               |
   +-----------------+-----------------+-----------------+-----------------+
   It is a natural generalization to make COUNT() identical to COUNT(*). So that's how Calcite represents COUNT(*) internally. 
   
   So the meaning of `count(*)` and counting first column are not always same because that the element of the first column may be null which will effect the result. 

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