MySQL 视图中的 Case 语句与 Union All

Question

我想向我的视图 "v_file_details" 添加一个 "Status" 列，该列将有一个值，具体取决于 "v_file_details.records_waiting_count" 和 "v_file_details.records_correct_count" 列中的数据。但是我不明白如何在视图中使用 Case？

create view v_file_details as
select 
fi.file_importer_id,
fi.file_name,
convert(time(0), fi.file_date) import_time,
fi.error_type,
((SELECT COUNT(*) From reservation Where file_importer_id = fi.file_importer_id AND status in ('S', 'S1')) + 
(SELECT COUNT(*) From error_file_record Where file_importer_id = fi.file_importer_id) +
(SELECT COUNT(*) From startup Where file_importer_id = fi.file_importer_id AND status in ('T', '6'))) as records_correct_count,
((SELECT COUNT(*) From location Where file_importer_id = fi.file_importer_id AND status = 'Y') + 
(SELECT COUNT(*) From reservation Where file_importer_id = fi.file_importer_id AND status = 'N') + 
(SELECT COUNT(*) From startup Where file_importer_id = fi.file_importer_id AND status in ('X', 'X1'))) as records_waiting_count,
case 'status' when records_waiting_count > 0 THEN 'Waiting' ELSE 'ACCEPTED', -- it is the problem, I don't know how to use CASE here
fi.new_file_name,

from file_importer fi
left join startup ts on fi.file_importer_id = ts.file_importer_id 
where ts.file_importer_id is not null

union all

select 
fi.file_importer_id,
fi.file_name,
convert(time(0), fi.file_date) import_time,
fi.error_type,
((SELECT COUNT(*) From reservation Where file_importer_id = fi.file_importer_id AND status in ('S', 'S1')) + 
(SELECT COUNT(*) From error_file_record Where file_importer_id = fi.file_importer_id) +
(SELECT COUNT(*) From startup Where file_importer_id = fi.file_importer_id AND status in ('T', '6'))) as records_correct_count,
((SELECT COUNT(*) From location Where file_importer_id = fi.file_importer_id AND status = 'Y') + 
(SELECT COUNT(*) From reservation Where file_importer_id = fi.file_importer_id AND status = 'N') + 
(SELECT COUNT(*) From startup Where file_importer_id = fi.file_importer_id AND status in ('X', 'X1'))) as records_waiting_count,
case 'status' when records_waiting_count > 0 THEN 'Waiting' ELSE 'ACCEPTED', --here the same
fi.new_file_name,

from file_importer fi
left join reservation res on fi.file_importer_id = res.file_importer_id 
where res.file_importer_id is not null

GO

Answer 1

您不能在 SELECT 中使用别名，因此您不能引用 records_waiting_count，您需要使用它所引用的表达式。此外，您已经有一个名为 status 的列，因此您不能调用 CASE 表达式的值（我们将其称为 waiting_status）。所以你的 CASE 表达式应该是这样的：

CASE WHEN ((SELECT COUNT(*) From location Where file_importer_id = fi.file_importer_id AND status = 'Y') + 
(SELECT COUNT(*) From reservation Where file_importer_id = fi.file_importer_id AND status = 'N') + 
(SELECT COUNT(*) From startup Where file_importer_id = fi.file_importer_id AND status in ('X', 'X1'))) > 0 THEN 'Waiting' ELSE 'Accepted' END AS waiting_status

MySQL 视图中的 Case 语句与 Union All

MySQL Case statement in a View with Union All

mysql

sql

case

union-all

sql-view