where age in () or age is null
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在后面添加 or age is null
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下拉框的数据集
SELECT (CASE WHEN isnull(age,'')='' THEN 'NULL' ELSE age END) [age] FROM text
表格数据集
SELECT * FROM text WHERE 1=1 ${IF(LEN(age)==0,""," and (CASE WHEN isnull(age,'')='' THEN 'NULL' ELSE age END) in ('"+age+"')")}