Question

由于某些原因，执行以下查询时出现以下错误：

您的SQL语法有错误;检查手册对应于您的MySQL服务器版本，以便使用正确的语法靠近＆＃39; ENGINE = FEDERATED＆＃39;第35行

CREATE TABLE users AS (
  SELECT
    ID, user_email, user_registered,
    first_name.meta_value as first_name,
    last_name.meta_value as last_name,
    telephone.meta_value as telephone,
    country.meta_value as country,
    company.meta_value as company,
    address.meta_value as address,
    city.meta_value as city,
    professional_title.meta_value as professional_title,
    state.meta_value as state,
    areas_of_interest.meta_value as areas_of_interest
    FROM wp_users
    LEFT JOIN wp_usermeta AS first_name ON first_name.user_id=ID
        AND first_name.meta_key='first_name'
    LEFT JOIN wp_usermeta AS last_name ON last_name.user_id=ID
        AND last_name.meta_key='last_name'
    LEFT JOIN wp_usermeta AS telephone ON telephone.user_id=ID
        AND telephone.meta_key='telephone'
    LEFT JOIN wp_usermeta AS country ON country.user_id=ID
        AND country.meta_key='country'
    LEFT JOIN wp_usermeta AS company ON company.user_id=ID
        AND company.meta_key='company'
    LEFT JOIN wp_usermeta AS address ON address.user_id=ID
        AND address.meta_key='address'
    LEFT JOIN wp_usermeta AS city ON city.user_id=ID
        AND city.meta_key='city'
    LEFT JOIN wp_usermeta AS professional_title ON professional_title.user_id=ID
        AND professional_title.meta_key='professional_title'
    LEFT JOIN wp_usermeta AS state ON state.user_id=ID
        AND state.meta_key='state'
    LEFT JOIN wp_usermeta AS areas_of_interest ON areas_of_interest.user_id=ID
        AND areas_of_interest.meta_key='areas_of_interest'
) ENGINE=FEDERATED DEFAULT CHARSET=latin1 CONNECTION "*****";

注意：已启用FEDERATED Engine并正在处理其他未连接的表。

Answer 1

简短回答：
FEDERATED表的CREATE语句需要一个称为CONNECTION的附加数据。语句中没有该数据是语法错误的来源。

答案很长：

对于这个特定的实例，VIEW将是一个比FEDERATED表更好的工具。

FEDERATED存储引擎虽然可以像Linux中的符号链接或Windows中的快捷方式。它主要用于访问服务器上的表，该表实际上并不在本地存储表，而是在不同的mysql服务器上。因此，在创建FEDERATED表时，还必须在CREATE语句中包含FEDERATED存储引擎应使用的CONNECTION。您可以选择在存储数据的同一主机上创建FEDERATED表，但这会导致因访问本地数据所采取的不必要步骤而导致的额外开销。有关详细信息，请参阅this link。

另一方面，VIEW就像一个存储的查询，只要您查询VIEW表就会执行该查询。 This page可以为您提供更多相关信息。

两个LEFT JOIN表的联合表不起作用

1 个答案: