SQLで「範囲」を設定するのに利用
例 日別で、salesの範囲を分ける
select ymd, shohin_id, sales , case when sales > 0 and sales <= 1000 then 1000 when sales > 1000 and sales <= 10000 then 10000 when sales > 10000 and sales <= 100000 then 100000 else '99999999' end as salse_dist from sales_tbl;
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