DESCRIBE

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

1. {DESCRIBE | DESC | EXPLAIN} tbl_name

参数说明

{DESCRIBE | DESC | EXPLAIN}

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

1. 表名，可指定表名。也可以指定schema_name.table_name。

示例

1. --创建test表
2. openGauss=# CREATE TABLE test2
3. openGauss-# (
4. openGauss(# id int PRIMARY KEY
5. openGauss(# );
6. NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test2_pkey" for table "test2"
7. CREATE TABLE
8. openGauss=# create table test
9. openGauss-# (
10. openGauss(# a SERIAL,
11. openGauss(# b varchar(10),
12. openGauss(# c varchar(10),
13. openGauss(# d varchar(10),
14. openGauss(# e varchar(10),
15. openGauss(# f varchar(10),
16. openGauss(# g varchar(10) DEFAULT 'g',
17. openGauss(# h varchar(10) NOT NULL,
18. openGauss(# i int DEFAULT 0,
19. openGauss(# j int DEFAULT 0,
20. openGauss(# k int GENERATED ALWAYS AS (i + j) STORED,
21. openGauss(# l int DEFAULT 0,
22. openGauss(# m int CHECK (m < 50),
23. openGauss(# PRIMARY KEY (a, b),
24. openGauss(# FOREIGN KEY(l) REFERENCES test2(id)
25. openGauss(# );
26. NOTICE:  CREATE TABLE will create implicit sequence "test_a_seq" for serial column "test.a"
27. NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test_pkey" for table "test"
28. CREATE TABLE
29. openGauss=# CREATE UNIQUE INDEX idx_c on test (c);
30. CREATE INDEX
31. openGauss=# CREATE UNIQUE INDEX idx_d_e on test (d, e);
32. CREATE INDEX
33. openGauss=# CREATE INDEX idx_f on test (f);
34. CREATE INDEX

36. --查看test表结构
37. openGauss=# desc test;
38. Field |         Type          | Null | Key |             Default             | Extra
39. -------+-----------------------+------+-----+---------------------------------+-------
40. a     | integer               | NO   | PRI | nextval('test_a_seq'::regclass) |
41. b     | character varying(10) | NO   | PRI | NULL                            |
42. c     | character varying(10) | YES  | UNI | NULL                            |
43. d     | character varying(10) | YES  | UNI | NULL                            |
44. e     | character varying(10) | YES  | UNI | NULL                            |
45. f     | character varying(10) | YES  | MUL | NULL                            |
46. g     | character varying(10) | YES  |     | 'g'::character varying          |
47. h     | character varying(10) | NO   |     | NULL                            |
48. i     | integer               | YES  |     | 0                               |
49. j     | integer               | YES  |     | 0                               |
50. k     | integer               | YES  |     | (i + j)                         |
51. l     | integer               | YES  | MUL | 0                               |
52. m     | integer               | YES  |     | NULL                            |
53. (13 rows)

55. openGauss=# desc public.test;
56. Field |         Type          | Null | Key |             Default             | Extra
57. -------+-----------------------+------+-----+---------------------------------+-------
58. a     | integer               | NO   | PRI | nextval('test_a_seq'::regclass) |
59. b     | character varying(10) | NO   | PRI | NULL                            |
60. c     | character varying(10) | YES  | UNI | NULL                            |
61. d     | character varying(10) | YES  | UNI | NULL                            |
62. e     | character varying(10) | YES  | UNI | NULL                            |
63. f     | character varying(10) | YES  | MUL | NULL                            |
64. g     | character varying(10) | YES  |     | 'g'::character varying          |
65. h     | character varying(10) | NO   |     | NULL                            |
66. i     | integer               | YES  |     | 0                               |
67. j     | integer               | YES  |     | 0                               |
68. k     | integer               | YES  |     | (i + j)                         |
69. l     | integer               | YES  | MUL | 0                               |
70. m     | integer               | YES  |     | NULL                            |
71. (13 rows)

73. openGauss=# describe public.test;
74. Field |         Type          | Null | Key |             Default             | Extra
75. -------+-----------------------+------+-----+---------------------------------+-------
76. a     | integer               | NO   | PRI | nextval('test_a_seq'::regclass) |
77. b     | character varying(10) | NO   | PRI | NULL                            |
78. c     | character varying(10) | YES  | UNI | NULL                            |
79. d     | character varying(10) | YES  | UNI | NULL                            |
80. e     | character varying(10) | YES  | UNI | NULL                            |
81. f     | character varying(10) | YES  | MUL | NULL                            |
82. g     | character varying(10) | YES  |     | 'g'::character varying          |
83. h     | character varying(10) | NO   |     | NULL                            |
84. i     | integer               | YES  |     | 0                               |
85. j     | integer               | YES  |     | 0                               |
86. k     | integer               | YES  |     | (i + j)                         |
87. l     | integer               | YES  | MUL | 0                               |
88. m     | integer               | YES  |     | NULL                            |
89. (13 rows)

DESCRIBE TABLE

DESCRIBE

功能描述

注意事项

语法格式

参数说明

示例

相关链接