Question

我有表存储每个实体（员工，部门）的详细信息。我想从该表构建动态查询。

CREATE TABLE MyTable
(
    Id int primary key,
    EntityId int,
    ColumnName varchar(100),
    tablename varchar(100)
);

INSERT INTO MyTable (Id, EntityId, ColumnName, tableName)
VALUES (1,1,'name','employee');

INSERT INTO MyTable (Id, EntityId, ColumnName, tableName)
VALUES (2,1,'id','employee');

INSERT INTO MyTable (Id, EntityId, ColumnName, tableName)
VALUES (3,1,'salary','employee');

INSERT INTO MyTable (Id, EntityId, ColumnName, tableName)
VALUES (4,2,'name','departement');

INSERT INTO MyTable (Id, EntityId, ColumnName, tableName)
VALUES (5,2,'location','departement');

INSERT INTO MyTable (Id, EntityId, ColumnName, tableName)
VALUES (6,2,'id','departement');

上面是我的表格和插入脚本，我怎样才能编写一个查询，它给出了类似下面的输出。

SELECT id,name,salary from employee

SELECT id,location,name from departement

如果我有多个实体，我应该多个选择语句。

Answer 1

如果尽管令人沮丧的评论仍然需要考虑这种方法，这里是每个实体构建一个查询的查询：

SELECT entityid,
  'SELECT ' ||
  string_agg(columnname, ', ' ORDER BY id) ||
  ' FROM ' ||
  tablename ||
  ';' AS query
FROM mytable
GROUP BY entityid, tablename;

您的示例结果：

 entityid |                   query                   
----------+---------------------------------------------
        1 | SELECT name, id, salary FROM employee;
        2 | SELECT name, location, id FROM departement;
(2 rows)

构建动态查询Postgres

1 个答案: