关于Mysql元数据如何生成Hive建表语句注释脚本

注：其他关系型数据库如：oracle 可以通过相同的思路，读取元数据，修改脚本语法实现。

使用：

在mysql元数据库：information_schema 中执行以下语句

SELECT CONCAT('alter table ', TABLE_NAME, ' CHANGE COLUMN ', COLUMN_NAME, ' ', COLUMN_NAME, ' ', DATA_TYPE, ' comment ', '"', COLUMN_COMMENT, '"', ';')
FROM (SELECT TABLE_NAME, COLUMN_NAME, CASE WHEN DATA_TYPE = 'varchar' THEN 'string' WHEN DATA_TYPE = 'int' THEN 'int' WHEN DATA_TYPE = 'tinyint' THEN 'tinyint' WHEN DATA_TYPE = 'decimal' THEN 'double' WHEN DATA_TYPE = 'datetime' THEN 'string' WHEN DATA_TYPE = 'timestamp' THEN 'string' WHEN DATA_TYPE = 'float' THEN 'double' WHEN DATA_TYPE = 'double' THEN 'double' WHEN DATA_TYPE = 'bigint' THEN 'bigint' END AS DATA_TYPE, COLUMN_COMMENT
FROM COLUMNS
WHERE TABLE_NAME = 'o_oms_statistic_profit'
) t;

在将数据从Mysql 等其他关系型数据库 抽取到Hive 表中时，需要同步mysql表中的注释，以下脚本可以生成hive创建表语句。只是生成了hive表主要的字段信息，其他信息需要手工添加。

在mysql元数据库：information_schema 中执行以下语句

SELECT CONCAT('create table ', TABLE_NAME, '(', substring(column_info, 1, length(column_info) - 1), ')', ' comment ', '"', TABLE_COMMENT, '"', ';')
FROM (SELECT TABLE_NAME, TABLE_COMMENT, group_concat(CONCAT(COLUMN_NAME, ' ', DATA_TYPE, ' comment ', '"', COLUMN_COMMENT, '"')) AS column_info
FROM (SELECT t1.TABLE_NAME, CASE WHEN t2.TABLE_COMMENT = NULL THEN t1.TABLE_NAME ELSE t2.TABLE_COMMENT END AS TABLE_COMMENT, COLUMN_NAME, CASE WHEN DATA_TYPE = 'varchar' THEN 'string' WHEN DATA_TYPE = 'int' THEN 'int' WHEN DATA_TYPE = 'tinyint' THEN 'tinyint' WHEN DATA_TYPE = 'decimal' THEN 'double' WHEN DATA_TYPE = 'datetime' THEN 'string' WHEN DATA_TYPE = 'timestamp' THEN 'string' WHEN DATA_TYPE = 'float' THEN 'double' WHEN DATA_TYPE = 'double' THEN 'double' WHEN DATA_TYPE = 'bigint' THEN 'bigint' END AS DATA_TYPE, CASE WHEN COLUMN_COMMENT = NULL THEN COLUMN_NAME ELSE COLUMN_COMMENT END AS COLUMN_COMMENT
FROM COLUMNS t1 JOIN TABLES t2 ON t1.TABLE_NAME = t2.TABLE_NAME
WHERE t1.TABLE_NAME = 'o_oms_statistic_profit'
) t3
GROUP BY TABLE_NAME, TABLE_COMMENT
) t4;

相关推荐：

什么叫MySQL元数据？元数据的介绍及实例代码

基于MySQL元数据的Hive的安装和简单测试

[MySQL] 获取元数据的步骤

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