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SELECT - select_clause

Quick Reference

Other versions: 7.31 | 7.40 | 7.54

Syntax


... [DISTINCT] select_list ...

Addition

... DISTINCT

Effect

SELECT clause of a query statement. The SELECT defines the structure of the results set of the SELECT statement. It consists of a SELECT list, which defines the columns of the results set, and an optional addition DISTINCT, which removes duplicative rows from the results set.

The SELECT list select_list can indicate all columns of a data source using * or it defines the individual columns of the results set using an SQL expression. It defines the names of the columns in the results set, using optional or mandatory alias names.


Note

The SELECT clause must either be listed as the first clause after the keyword SELECT (or after the optional addition SINGLE) or after the FROM clause. After the FROM clause, the SELECT clause must be introduced using the addition FIELDS. A FROM clause of the SELECT clause supports tools such as the code completion in ABAP Editor.


Example

SELECT clause after FIELDS, whose SELECT list specifies individual columns plus aggregate expressions as arguments using SQL expressions.

SELECT FROM sflight 
       FIELDS carrid, 
              connid, 
              MAX( seatsmax - seatsocc ) AS seatsfree_max, 
              MIN( seatsmax - seatsocc ) AS seatsfree_min 
       GROUP BY carrid, connid 
       HAVING carrid = 'LH' 
       INTO TABLE @DATA(result).

Addition

... DISTINCT

Effect

The addition DISTINCT removes rows that occur more than once in a multirow results set. Here the entire row content is taken into consideration.

The addition DISTINCT must not be used in the following cases:

  • If the addition SINGLE is used.
  • If a column specified in the SELECT list select_list has the type STRING, RAWSTRING, LCHR, LRAW, or GEOM_EWKB.

If DISTINCT is used, the statement SELECT bypasses table buffering.


Notes

  • For the addition DISTINCT, it is not important which columns of the results set are key fields of the associated database tables, views, or CDS entities.
  • The comparison is based on the full row content, which means that the number of rows in the results set is determined by the SELECT list. If, for example, all key fields of a database table are specified directly as columns in a SELECT list, there can be no rows that occur more than once. The other extreme is the case where a SELECT list contains a single host variable or a single literal. Here, all rows are deleted except one.
  • As a part of the SELECT clause, the addition DISTINCT is applied before the additions UP TO and OFFSET are evaluated.
  • If DISTINCT is specified, it should be noted that this requires the execution of sort operations in the database system, and the statement SELECT therefore bypasses table buffering.


Example

Gets all destinations to which Lufthansa flies from Frankfurt.

SELECT DISTINCT cityto 
       FROM spfli 
       WHERE carrid = 'LH' AND 
             cityfrom = 'FRANKFURT' 
       INTO TABLE @DATA(destinations). 

cl_demo_output=>display( destinations ).

Continue

SELECT - select_list