This query fails:
此查询失败：
SELECT xpath('/my/xpath/expr', my_xml)[1] FROM my_table
ERROR: syntax error at or near "["
But this one works:
但是这个有效：
SELECT x[1] FROM
(SELECT xpath('/my/xpath/expr', my_xml) as x FROM my_table) as ss
My xpath expression always returns only a single value, but the Postgres xpath function returns an array. I want to select the first value in the array. While the subselect works, it's pretty ugly.
我的xpath表达式总是只返回一个值，但Postgres xpath函数返回一个数组。我想选择数组中的第一个值。虽然subselect有效，但它非常难看。
Why doesn't the first query work, and is there a cleaner way to do this than the second query?
为什么第一个查询不起作用，是否有比第二个查询更简洁的方法？
1 个解决方案
#1
7
How about this:
这个怎么样：
SELECT (xpath('/my/xpath/expr', my_xml))[1] FROM my_table;
#1
7
How about this:
这个怎么样：
SELECT (xpath('/my/xpath/expr', my_xml))[1] FROM my_table;