mysql怎么查看表结构及已有索引信息

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查看表结构及已有索引信息

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：

desc tableName; desc employees.employees;
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show columns from tableName; show COLUMNS from employees.employees;

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。

show create table tableName; show CREATE TABLE employees.employees;

这个语句会显示这个表的建表语句。

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：

01
## 查看所有的库
02
SELECT
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lower(schema_name) schema_name
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FROM
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information_schema.schemata
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WHERE
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schema_name NOT IN (
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mysql ,
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information_schema ,
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test ,
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search ,
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tbsearch ,
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sbtest ,
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dev_ddl
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)
16

17
## 产看某一个库中的所有表
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SELECT
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table_name,
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create_time updated_at,
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table_type,
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ENGINE,
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table_rows num_rows,
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table_comment,
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ceil(data_length / 1024 / 1024) store_capacity
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FROM
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information_schema.TABLES
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WHERE
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table_schema = employees
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AND table_name NOT LIKE tmp#_% ESCAPE #
31

32
## 查看某一个库下某一个表的所有字段
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SELECT
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lower(column_name) column_name,
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ordinal_position position,
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column_default dafault_value,
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substring(is_nullable, 1, 1) nullable,
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column_type data_type,
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column_comment,
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character_maximum_length data_length,
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numeric_precision data_precision,
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numeric_scale data_scale
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FROM
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information_schema.COLUMNS
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WHERE
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table_schema = employees
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AND table_name = employees
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49

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## 查看某一个库下某一张表的索引
51

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SELECT DISTINCT
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lower(index_name) index_name,
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lower(index_type) type
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FROM
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information_schema.statistics
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WHERE
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table_schema = employees
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AND table_name = employees
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61
## 查看某一个库下某一张表的某一个索引
62

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SELECT
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lower(column_name) column_name,
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seq_in_index column_position
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FROM
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information_schema.statistics
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WHERE
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table_schema = employees
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AND table_name = employees
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AND index_name = primary
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73
## 查看某一个库下某一个表的注释
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SELECT
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table_comment comments
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FROM
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information_schema.TABLES
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WHERE
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table_schema = employees
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AND table_name = employees
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## 查看某一个库下某一个表的列的注释
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SELECT
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lower(column_name) column_name,
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column_comment comments
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FROM
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COLUMNS
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WHERE
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table_schema = employees
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AND table_name = employees
oracle 部分：
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001
#table structure:
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SELECT
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lower(table_name) table_name,
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TEMPORARY,
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tablespace_name,
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num_rows,
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duration,
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ORACLE table_type,
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partitioned,
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(
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SELECT
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ceil(sum(bytes) / 1024 / 1024)
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FROM
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dba_segments b
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WHERE
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a. OWNER = b. OWNER
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AND a.table_name = b.segment_name
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) AS store_capacity
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FROM
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dba_tables a
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WHERE
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OWNER = ?
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AND table_name NOT LIKE TMP%
024

025
SELECT
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lower(column_name) column_name,
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column_id position,
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data_type,
029
data_length,
030
data_precision,
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data_scale,
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nullable,
033
data_default default_value,
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default_length
035
FROM
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dba_tab_columns
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WHERE
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OWNER = ?
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AND table_name = ?;
040

041
# index
042
SELECT
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lower(index_name) index_name,
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index_type type
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FROM
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dba_indexes
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WHERE
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OWNER = ?
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AND table_name = ?
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AND index_name NOT LIKE SYS_IL%
051

052
SELECT
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lower(column_name) column_name,
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column_position,
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descend
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FROM
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dba_ind_columns
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WHERE
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table_owner = ?
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AND table_name = ?
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AND index_name = ?;
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063
#collect description
064
SELECT
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comments
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FROM
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dba_tab_comments
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WHERE
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OWNER = ?
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AND table_name = ?;
071

072
SELECT
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lower(column_name) column_name,
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comments
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FROM
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dba_col_comments
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WHERE
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OWNER = ?
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AND table_name = ?;
080

081
#database
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SELECT
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lower(username) username
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FROM
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dba_users
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WHERE
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username NOT IN (
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STDBYPERF ,
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READONLY ,
090
APPQOSSYS ,
091
ANYSQL ,
092
DBFLASH ,
093
SYS ,
094
SYSTEM ,
095
MONITOR ,
096
TBSEARCH ,
097
MANAGER ,
098 www.2cto.com
SYSMAN ,
099
EXFSYS ,
100
WMSYS ,
101
DIP ,
102
TSMSYS ,
103
ORACLE_OCM ,
104
OUTLN ,
105
DBSNMP ,
106
PERFSTAT ,
107
SEARCH ,
108
TOOLS ,
109
TBDUMP ,
110
DMSYS ,
111
XDB ,
112
ANONYMOUS ,
113
DEV_DDL
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);
115

116
#segsize
117
SELECT
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round(sum(bytes) / 1024 / 1024, 0) mbytes
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FROM
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dba_segments
121
WHERE
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OWNER = ?
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AND segment_name = ?;
关于 oralce 中的 segements，可以参考一下这个系列文章。