在MySQL下运行完下面这个建表语句后。 如何从数据字典中，检索出这个表的字段的相关信息？
DROP TABLE IF EXISTS test_table;
CREATE TABLE test_table(
Test_ID int NOT NULL AUTO_INCREMENT PRIMARY KEY COMMENT ‘主键(自增长)’ ,
Test_Key varchar(10) NOT NULL COMMENT ‘种类’ ,
Test_Value varchar(20) NOT NULL COMMENT ’数值’ ,
Test_Type int NOT NULL COMMENT ‘内部类型’ ,
Test_BelongTo int COMMENT ‘从属关系’ ,
Test_Grade int DEFAULT 1 COMMENT ’等级’ ,
Test_Remark varchar(50) COMMENT ‘备注’ ,
Test_Visible bit DEFAULT 1 COMMENT ‘是否可见’
)
COMMENT = ‘测试表’;
答案是：
SELECT
column_name AS `列名`,
data_type AS `数据类型`,
character_maximum_length AS `字符长度`,
numeric_precision AS `数字长度`,
numeric_scale AS `小数位数`,
is_nullable AS `是否允许非空`,
CASE WHEN extra = ‘auto_increment’
THEN 1 ELSE 0 END AS `是否自增`,
column_default AS `默认值`,
column_comment AS `备注`
FROM
Information_schema.columns
WHERE
table_Name=’test_table’;