Question

我正在尝试简化以下最终声明：

DROP TABLE asdf;

CREATE TABLE asdf (LIKE calibrations);

INSERT INTO asdf (rid, pid, status, cal_date, project_name, username,
  sensor_type, serial_number, var_name, dsm_name, cal_type, channel,
  gainbplr, ads_file_name, set_times, set_points, averages, stddevs, cal,
  temperature, comment)
  SELECT * FROM dblink(
    'host=remoteserv user=auser password=hello dbname=cals',
    'SELECT * FROM calibrations WHERE username=\'JAM\'') AS
      t(rid character varying(20), pid character varying(20),
        status character(3), cal_date timestamp,
        project_name character varying(32), username character varying(32),
        sensor_type character varying(20), sn character varying(20),
        var_name character varying(20), dsm_name character varying(16),
        cal_type character varying(16), channel character(1),
        gainbplr character(2), ads_file_name character varying(40),
        set_times timestamp[], set_points double precision[],
        averages double precision[], stddevs double precision[],
        cal double precision[], temperature double precision,
        comment character varying(256));

我能够简化最后一句话：

INSERT INTO asdf 
  SELECT * FROM dblink(
    'host=remoteserv user=auser password=hello dbname=cals',
    'SELECT * FROM calibrations WHERE username=\'JAM\'') AS
      t(rid character varying(20), pid character varying(20),
        status character(3), cal_date timestamp,
        project_name character varying(32), username character varying(32),
        sensor_type character varying(20), sn character varying(20),
        var_name character varying(20), dsm_name character varying(16),
        cal_type character varying(16), channel character(1),
        gainbplr character(2), ads_file_name character varying(40),
        set_times timestamp[], set_points double precision[],
        averages double precision[], stddevs double precision[],
        cal double precision[], temperature double precision,
        comment character varying(256));

是否可以将最后一个语句写成这样的东西？

INSERT INTO asdf 
  SELECT * FROM dblink(
    'host=remoteserv user=auser password=hello dbname=cals',
    'SELECT * FROM calibrations WHERE username=\'JAM\'') AS
      t(LIKE calibrations);

- 约翰

Answer 1

不，dblink（）函数返回setof record，数据库需要知道列列表。这在dblink文档中提到：

该函数返回查询生成的行。由于dblink可以使用任何查询，都声明它返回记录，而不是指定任何特定的一组列。这意味着您必须在中指定预期的列集调用查询 - 否则PostgreSQL不知道会发生什么。

FROM语句的SELECT子句具有以下定义：

where from_item can be one of:

    [ ONLY ] table_name [ * ] [ [ AS ] alias [ ( column_alias [, ...] ) ] ]
    ( select ) [ AS ] alias [ ( column_alias [, ...] ) ]
    with_query_name [ [ AS ] alias [ ( column_alias [, ...] ) ] ]
    function_name ( [ argument [, ...] ] ) [ AS ] alias [ ( column_alias [, ...] | column_definition [, ...] ) ]
    function_name ( [ argument [, ...] ] ) AS ( column_definition [, ...] )
    from_item [ NATURAL ] join_type from_item [ ON join_condition | USING ( join_column [, ...] ) ]

在INSERT语句中使用“LIKE”来描述dblink的SELECT语句中的记录

1 个答案: