在有条件的情况下使用 case 时出现语法错误

Question

我收到以下错误：

postgresql 错误：“2020”或附近的语法错误第 2 行：... THEN 金额 * split_exchange_rate ELSE 0 END) AS 2020Q4_rev...

见下面的代码。我正在使用 postgresql

SELECT object_id
  , SUM(CASE WHEN created::date >= '2020-10-01' AND created::date <= '2020-12-31' THEN amount * exchange_rate ELSE 0 END) AS 2020Q4_revenue
  , SUM(CASE WHEN created::date >= '2021-01-01' AND created::date <= '2021-03-31' THEN amount * exchange_rate ELSE 0 END) AS 2021Q1_revenue
  , SUM(CASE WHEN created::date >= '2021-04-01' AND created::date <= '2021-06-30' THEN amount * exchange_rate ELSE 0 END) AS 2021Q2_revenue
  , SUM(CASE WHEN created::date >= '2021-07-01' AND created::date <= '2021-09-30' THEN amount * exchange_rate ELSE 0 END) AS 2021Q3_revenue
from raw_data.purchase_revenue pr
group by 1

Answer 1

像2020Q4_revenue这样的别名是SQL中的“标识符”，所以它必须符合the rules:

SQL identifiers and key words must begin with a letter (a-z, but also letters with diacritical marks and non-Latin letters) or an underscore (_). Subsequent characters in an identifier or key word can be letters, underscores, digits (0-9), or dollar signs ($). Note that dollar signs are not allowed in identifiers according to the letter of the SQL standard, so their use might render applications less portable.

如果用双引号引用该别名，您仍然可以使用它：

There is a second kind of identifier: the delimited identifier or quoted identifier. It is formed by enclosing an arbitrary sequence of characters in double-quotes ("). A delimited identifier is always an identifier, never a key word. So "select" could be used to refer to a column or table named “select”, whereas an unquoted select would be taken as a key word and would therefore provoke a parse error when used where a table or column name is expected.

Quoted identifiers can contain any character, except the character with code zero. (To include a double quote, write two double quotes.)

在有条件的情况下使用 case 时出现语法错误

Syntax Error when using a case when conditional

postgresql

column-alias