如何在 python 中使用 case 语句

Question

我有一部分代码检查零并给出通过或失败

l=[dbname,tbname,python,fact, game_table]
f_query  = "select case when count(*)=1 then 'Pass' else 'Fail' end result"
f_query += " from  qa."+row.DB_NAME
f_query += " where "+ row.Field_NAME + "=0"

如何在此代码中包含另一个 when 语句，我需要从具有 l=[dbname,tbname,python,fact, game_table] 的列表或元组中获取 row.DB_NAME 但是当它们存在时，结果应该成为'exp'。 所以，我尝试了这样的事情：

l=[dbname,tbname,python,fact, game_table]
f_query  = "select case when count(*)=1 then 'Pass' when row.DB_Name in l then 'exp'
            else 'Fail' end result"
f_query += " from  qa."+row.DB_NAME
f_query += " where "+ row.Field_NAME + "=0"

但这不起作用。 有人可以帮我弄这个吗

Answer 1

您可以将列表加入字符串并使用表别名将 SQL 拼接在一起：

l=[dbname,tbname,python,fact, game_table]
f_query  = "select case when count(*)=1 then 'Pass'"
f_query += " when t1 in ({}) then 'exp'".format(','.join(l))
f_query += " else 'Fail' end result"
f_query += " from qa."+row.DB_NAME+" as t1"
f_query += " where "+ row.Field_NAME + "=0"