mysql查看表结构信息需求背景是给一个表名然后给出相应的表结构信息及索引信息 常用的命令有如下： 1. desc tableName; desc employees.employees; 2. sh

需求背景是给一个表名然后给出相应的表结构信息及索引信息
常用的命令有如下：
1. desc tableName; desc employees.employees;
2. show columns from tableName; show COLUMNS from employees.employees;
3. describe tableName; DESCRIBE employees.employees;
这三个显示的结果都是一样的，显示表中filed，type，null，key，default及extra。
4. show create table tableName; show CREATE TABLE employees.employees;
这个语句会显示这个表的建表语句。
5. select * from columns where table_name='表名';select * from information_schema.COLUMNS where TABLE_SCHEMA='employees' and TABLE_NAME='employees';
这个显示的结果就比较全了。
接下来，来点更全的sql，这个是用来同步mysql和orac数据字典的所有sql。
mysql部分：
## 查看所有的库
SELECT
    lower(schema_name) schema_name
FROM
    information_schema.schemata
WHERE
    schema_name NOT IN (
        'mysql',
        'information_schema',
        'test',
        'search',
        'tbsearch',
        'sbtest',
        'dev_ddl'
    )
 
## 产看某一个库中的所有表
SELECT
    table_name,
    create_time updated_at,
    table_type,
    ENGINE,
    table_rows num_rows,
    table_comment,
    ceil(data_length / 1024 / 1024) store_capacity
FROM
    information_schema.TABLES
WHERE
    table_schema = 'employees'
AND table_name NOT LIKE 'tmp#_%' ESCAPE '#'
 
##查看某一个库下某一个表的所有字段
SELECT
    lower(column_name) column_name,
    ordinal_position position,
    column_default dafault_value,
    substring(is_nullable, 1, 1) nullable,
    column_type data_type,
    column_comment,
    character_maximum_length data_length,
    numeric_precision data_precision,
    numeric_scale data_scale
FROM
    information_schema.COLUMNS
WHERE
    table_schema = 'employees'
AND table_name = 'employees';
 
 
## 查看某一个库下某一张表的索引
 
SELECT DISTINCT
    lower(index_name) index_name,
    lower(index_type) type
FROM
    information_schema.statistics
WHERE
    table_schema = 'employees'
AND table_name = 'employees';
 
## 查看某一个库下某一张表的某一个索引
 
SELECT
    lower(column_name) column_name,
    seq_in_index column_position
FROM
    information_schema.statistics
WHERE
    table_schema = 'employees'
AND table_name = 'employees'
AND index_name = 'primary';
 
## 查看某一个库下某一个表的注释
SELECT
    table_comment comments
FROM
    information_schema.TABLES
WHERE
    table_schema = 'employees'
AND table_name = 'employees';
 
## 查看某一个库下某一个表的列的注释
SELECT
    lower(column_name) column_name,
    column_comment comments
FROM
    COLUMNS
WHERE
    table_schema = 'employees'
AND table_name = 'employees';