Question

我有一个名为借项的表，其中包含许多字段，例如（id，名称，描述等）。在该表中，我有一列，其类型为JSON（TermsMessage）（JSON数组），何时我进行选择查询，返回错误

我的查询

`

  select 
    z.loan_id, 
    z.loan_name, 
    z.max_amount, 
    z.min_amount,
        z.min_age,
        z.max_age,
        z.min_loan_term,
        z.max_loan_term,
        z.TermsMessage,
    to_json(array_agg(distinct z.jsjs)) as aims,
    to_json(array_agg(distinct z.jsjs1)) as cities,
    from(
        select 
        c.loan_id, 
        c.loan_name, 
        c.max_amount,
        c.min_amount,
        c.min_age,
        c.max_age,
        c.min_loan_term,
        c.max_loan_term,
        c.TermsMessage,
        ( select x from (select c.aim_id, c.aim_name) x) as jsjs,
        ( select x from (select c.city_id, c.city_name) x) as jsjs1
        from 
        ( select 
        l.id as loan_id, 
        l.name as loan_name, 
        l.max_amount, 
        l.min_amount,
        l.min_age,
        l.max_age,
        l.min_loan_term,
        l.max_loan_term,
        l.TermsMessage,
        --
        a.id as aim_id, 
        a.name as aim_name,
        --
        c.id as city_id,
        c.name as city_name
        --
        from loans as l
        left join loan_aims as la on la._loan = l.id
        left join aims as a on a.id = la._aim
        ------------
        left join loan_cities as lc on lc._loan=l.id
        left join cities as c on c.id = lc._city
        ------------

        ) c     
    ) z
    group by z.loan_id,
        z.loan_name, 
        z.max_amount,
        z.min_amount,
        z.min_age,
        z.max_age,
        z.min_loan_term,
        z.max_loan_term;

`

termsMessage必须出现在GROUP BY子句中或在聚合函数中使用

当我将JSON列添加到GROUP BY时，它返回另一个错误

 group by z.loan_id,
            z.loan_name, 
            z.max_amount,
            z.min_amount,
            z.min_age,
            z.max_age,
            z.min_loan_term,
            z.max_loan_term,
            z.TermsMessage;

无法识别json类型的相等运算符

Answer 1

对于数据类型JSON或JSON数组，PostgreSQL没有内置的相等运算符。在按JSON字段分组时，数据库需要知道哪些是相同的值并且可以分组在一起。您可以使用:: jsonb []或:: text []将JSON（或JSON数组）转换为文本数组或JSONb数组来解决此问题。我可能会在查询的最内部进行操作，以使其自然地流过以后：

  select 
    z.loan_id, 
    z.loan_name, 
    z.max_amount, 
    z.min_amount,
        z.min_age,
        z.max_age,
        z.min_loan_term,
        z.max_loan_term,
        z.TermsMessage,
    to_json(array_agg(distinct z.jsjs)) as aims,
    to_json(array_agg(distinct z.jsjs1)) as cities,
    from(
        select 
        c.loan_id, 
        c.loan_name, 
        c.max_amount,
        c.min_amount,
        c.min_age,
        c.max_age,
        c.min_loan_term,
        c.max_loan_term,
        c.TermsMessage,
        ( select x from (select c.aim_id, c.aim_name) x) as jsjs,
        ( select x from (select c.city_id, c.city_name) x) as jsjs1
        from 
        ( select 
        l.id as loan_id, 
        l.name as loan_name, 
        l.max_amount, 
        l.min_amount,
        l.min_age,
        l.max_age,
        l.min_loan_term,
        l.max_loan_term,
        l.TermsMessage::jsonb[] as TermsMessage ,
        --
        a.id as aim_id, 
        a.name as aim_name,
        --
        c.id as city_id,
        c.name as city_name
        --
        from loans as l
        left join loan_aims as la on la._loan = l.id
        left join aims as a on a.id = la._aim
        ------------
        left join loan_cities as lc on lc._loan=l.id
        left join cities as c on c.id = lc._city
        ------------

        ) c     
    ) z
    group by z.loan_id,
        z.loan_name, 
        z.max_amount,
        z.min_amount,
        z.min_age,
        z.max_age,
        z.min_loan_term,
        z.max_loan_term,
        z.TermsMessage;

如何从表格Postgres中选择json

1 个答案: