DESCRIBE

功能描述

DESCRIBE 和 EXPLAIN 互为同义词，可以用于查看指定表结构，或查看指定 SQL 的执行计划。

查看执行计划部分内容详见 EXPLAIN。

注意事项

临时表需要指定临时表对应的schema查询。
复合主键索引所有参与列都会在Key字段中显示为PRI。
复合唯一索引所有参与列都会在Key字段中显示为UNI。
如果一个列参与了多个索引的创建，将按 PRI、UNI、MUL 的优先级顺序显示。
生成列会在Default中显示生成式。
不支持表同义词。

语法格式

{DESCRIBE | DESC | EXPLAIN} tbl_name

参数说明

{DESCRIBE | DESC | EXPLAIN}

使用 DESCRIBE、DESC 和 EXPLAIN 效果是等价的。
tbl_name

表名，可指定表名。也可以指定schema_name.table_name。

示例

--创建test表
MogDB=# CREATE TABLE test2
MogDB-# (
MogDB(# id int PRIMARY KEY
MogDB(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test2_pkey" for table "test2"
CREATE TABLE
MogDB=# create table test
MogDB-# (
MogDB(# a SERIAL,
MogDB(# b varchar(10),
MogDB(# c varchar(10),
MogDB(# d varchar(10),
MogDB(# e varchar(10),
MogDB(# f varchar(10),
MogDB(# g varchar(10) DEFAULT 'g',
MogDB(# h varchar(10) NOT NULL,
MogDB(# i int DEFAULT 0,
MogDB(# j int DEFAULT 0,
MogDB(# k int GENERATED ALWAYS AS (i + j) STORED,
MogDB(# l int DEFAULT 0,
MogDB(# m int CHECK (m < 50),
MogDB(# PRIMARY KEY (a, b),
MogDB(# FOREIGN KEY(l) REFERENCES test2(id)
MogDB(# );
NOTICE:  CREATE TABLE will create implicit sequence "test_a_seq" for serial column "test.a"
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test_pkey" for table "test"
CREATE TABLE
MogDB=# CREATE UNIQUE INDEX idx_c on test (c);
CREATE INDEX
MogDB=# CREATE UNIQUE INDEX idx_d_e on test (d, e);
CREATE INDEX
MogDB=# CREATE INDEX idx_f on test (f);
CREATE INDEX

--查看test表结构
MogDB=# desc test;
 Field |         Type          | Null | Key |             Default             | Extra
-------+-----------------------+------+-----+---------------------------------+-------
 a     | integer               | NO   | PRI | nextval('test_a_seq'::regclass) |
 b     | character varying(10) | NO   | PRI | NULL                            |
 c     | character varying(10) | YES  | UNI | NULL                            |
 d     | character varying(10) | YES  | UNI | NULL                            |
 e     | character varying(10) | YES  | UNI | NULL                            |
 f     | character varying(10) | YES  | MUL | NULL                            |
 g     | character varying(10) | YES  |     | 'g'::character varying          |
 h     | character varying(10) | NO   |     | NULL                            |
 i     | integer               | YES  |     | 0                               |
 j     | integer               | YES  |     | 0                               |
 k     | integer               | YES  |     | (i + j)                         |
 l     | integer               | YES  | MUL | 0                               |
 m     | integer               | YES  |     | NULL                            |
(13 rows)

MogDB=# desc public.test;
 Field |         Type          | Null | Key |             Default             | Extra
-------+-----------------------+------+-----+---------------------------------+-------
 a     | integer               | NO   | PRI | nextval('test_a_seq'::regclass) |
 b     | character varying(10) | NO   | PRI | NULL                            |
 c     | character varying(10) | YES  | UNI | NULL                            |
 d     | character varying(10) | YES  | UNI | NULL                            |
 e     | character varying(10) | YES  | UNI | NULL                            |
 f     | character varying(10) | YES  | MUL | NULL                            |
 g     | character varying(10) | YES  |     | 'g'::character varying          |
 h     | character varying(10) | NO   |     | NULL                            |
 i     | integer               | YES  |     | 0                               |
 j     | integer               | YES  |     | 0                               |
 k     | integer               | YES  |     | (i + j)                         |
 l     | integer               | YES  | MUL | 0                               |
 m     | integer               | YES  |     | NULL                            |
(13 rows)

MogDB=# describe public.test;
 Field |         Type          | Null | Key |             Default             | Extra
-------+-----------------------+------+-----+---------------------------------+-------
 a     | integer               | NO   | PRI | nextval('test_a_seq'::regclass) |
 b     | character varying(10) | NO   | PRI | NULL                            |
 c     | character varying(10) | YES  | UNI | NULL                            |
 d     | character varying(10) | YES  | UNI | NULL                            |
 e     | character varying(10) | YES  | UNI | NULL                            |
 f     | character varying(10) | YES  | MUL | NULL                            |
 g     | character varying(10) | YES  |     | 'g'::character varying          |
 h     | character varying(10) | NO   |     | NULL                            |
 i     | integer               | YES  |     | 0                               |
 j     | integer               | YES  |     | 0                               |
 k     | integer               | YES  |     | (i + j)                         |
 l     | integer               | YES  | MUL | 0                               |
 m     | integer               | YES  |     | NULL                            |
(13 rows)

DESCRIBE

功能描述

注意事项

语法格式

参数说明

示例

相关链接