oracle 字符集不匹配
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Character set mismatch
提问by
I have a SQL statement like this:
我有一个这样的 SQL 语句：
SELECT
a.ColumnA, b.ColumnB ||
CASE WHEN TRIM(c.ColumnC) IS NOT NULL THEN ' (' || c.ColumnC || ')' ELSE '' END AS ClassName
FROM TableA a INNER JOIN TableB b ON a.SomeColumn = b.SomeColumn
INNER JOIN TableC c on a.SomeCol = c.SomeCol
I'm getting an error "Character set mismatch" at the " ELSE '' " part of the CASE expression. Can someone suggest where I'm doing it wrong? Thank you.
我在 CASE 表达式的“ ELSE '' ”部分收到错误“字符集不匹配”。有人可以建议我在哪里做错了吗？谢谢你。
回答by Adam Hawkes
You cannot concatenate VARCHAR and NVARCHAR values without a CAST statement.
您不能在没有 CAST 语句的情况下连接 VARCHAR 和 NVARCHAR 值。
回答by Matt Birchall
CASE WHEN TRIM(c.ColumnC) IS NOT NULL
THEN ' (' || c.ColumnC || ')'
ELSE N'' END A
is a more concise solution. N'' gives you a unicode empty string
是一个更简洁的解决方案。N'' 给你一个 unicode 空字符串
回答by Roger
Just erase the ELSE, would make your code easier to read
只需擦除 ELSE，将使您的代码更易于阅读
回答by jva
Did you try replacing '' with NULL? Also, try removing ELSE part altogether because it will return NULL anyway.
您是否尝试将 '' 替换为 NULL？此外，尝试完全删除 ELSE 部分，因为它无论如何都会返回 NULL。
