如何在 PostgreSQL (9.1) 函数中将字符转换为整数？
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How do I convert a character to integer within a PostgreSQL (9.1) function?
提问by Georgy Passos
I have this following code:
我有以下代码：
BEGIN
x := split_part(text, ',', 1);
UPDATE albumphoto SET order = 1 WHERE idtable = 1 AND idx = x;
END
But my column table named idxis a numeric type, and the split_partreturns a character type to the variable x. I've tried using CAST, but I don't know how to use it properly.
但是我命名的列表idx是数字类型，并且split_part将字符类型返回给变量x。我试过使用CAST，但我不知道如何正确使用它。
Any ideas?
有任何想法吗？
回答by Anton Kovalenko
Like this:
像这样：
UPDATE albumphoto SET order = 1 WHERE idtable = 1 AND idx = CAST (x AS INTEGER);
(Use appropriate numeric type instead of INTEGER).
（使用适当的数字类型而不是INTEGER）。
回答by Erwin Brandstetter
Or simpler:
或者更简单：
UPDATE albumphoto
SET order = 1
WHERE idtable = 1
AND idx = split_part(text, ',', 1)::int -- or whatever type it is
AND order IS DISTINCT FROM 1;
expression::typeis the simple (non-SQL-standard) Postgres way to cast. Details in the manual in the chapter Type Casts.
More about data types in PostgreSQL.
expression::type是简单的（非 SQL 标准的）Postgres 转换方式。Type Casts一章的手册中的详细信息。
更多关于PostgreSQL 中的数据类型。
The last predicate I added is useful if ordercould already be1, in which case the update wouldn't change anything, but still cost the same. Rather do nothing instead. Related (consider the last paragraph):
如果我说的最后断言是有用的order可能已经是1，在这种情况下，更新不会改变什么，但费用仍然是相同的。而是什么都不做。相关（考虑最后一段）：
And you don't needa variable here.
而且这里不需要变量。
