SHOW COLUMNS
功能描述
查看指定表的列元信息。
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,以该列第一个创建的索引为准显示Key字段。
- 生成列会在Default中显示生成式。
- 表名中含schemaname/dbname并且同时指定dbname时,仅匹配指定的dbname。
- 结果仅显示当前查询用户具有SELECT权限的列信息。
语法格式
SHOW [FULL] {COLUMNS | FIELDS}
{FROM | IN} tbl_name
[{FROM | IN} db_name]
[LIKE 'pattern' | WHERE expr]
参数说明
{COLUMNS | FIELDS}
使用COLUMNS和FIELDS效果是等价的。
tbl_name
表名,可指定表名。也可以指定schema_name.table_name。
db_name
库名(或schema),当tbl_name中也指定库名(或schema名)时,优先选择本选项。
LIKE 'pattern'
pattern匹配显示结果的Field列。
示例
--创建简单表
openGauss=# CREATE SCHEMA tst_schema1;
openGauss=# SET SEARCH_PATH TO tst_schema1;
openGauss=# CREATE TABLE tst_t1
openGauss-# (
openGauss(# id int primary key,
openGauss(# name varchar(20) NOT NULL,
openGauss(# addr text COLLATE "de_DE",
openGauss(# phone text COLLATE "es_ES",
openGauss(# addr_code text
openGauss(# );
openGauss=# COMMENT ON COLUMN tst_t1.id IS 'identity';
--查看表的列元信息
openGauss=# SHOW COLUMNS FROM tst_t1;
Field | Type | Null | Key | Default | Extra
-----------+-----------------------+------+-----+---------+-------
id | integer | NO | PRI | NULL |
name | character varying(20) | NO | | NULL |
addr | text | YES | | NULL |
phone | text | YES | | NULL |
addr_code | text | YES | | NULL |
openGauss=# show FULL COLUMNS FROM tst_t1;
Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment
-----------+-----------------------+-----------+------+-----+---------+-------+-----------------------------------------+----------
id | integer | NULL | NO | PRI | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT | identity
name | character varying(20) | NULL | NO | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
addr | text | de_DE | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
phone | text | es_ES | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
addr_code | text | NULL | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
openGauss=# show FULL COLUMNS FROM tst_schema1.tst_t1;
Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment
-----------+-----------------------+-----------+------+-----+---------+-------+-----------------------------------------+----------
id | integer | NULL | NO | PRI | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT | identity
name | character varying(20) | NULL | NO | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
addr | text | de_DE | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
phone | text | es_ES | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
addr_code | text | NULL | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
--模糊匹配、过滤
openGauss=# show full columns from tst_t1 like '%addr%';
Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment
-----------+------+-----------+------+-----+---------+-------+-----------------------------------------+---------
addr | text | de_DE | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
addr_code | text | NULL | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
openGauss=# show full columns from tst_t1 where Type='text';
Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment
-----------+------+-----------+------+-----+---------+-------+-----------------------------------------+---------
addr | text | de_DE | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
phone | text | es_ES | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
addr_code | text | NULL | YES | | NULL | | UPDATE,SELECT,REFERENCES,INSERT,COMMENT |
--显示权限过滤
openGauss=# CREATE USER tst_u1 PASSWORD 'tst_u1@123';
openGauss=# SET ROLE tst_u1 PASSWORD 'tst_u1@123';
opengauss=> SET SEARCH_PATH TO tst_schema1;
openGauss=> show full columns from tst_t1;
Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment
-------+------+-----------+------+-----+---------+-------+------------+---------
(0 rows)
openGauss=# RESET ROLE;
opengauss=# GRANT SELECT (addr, phone) on tst_t1 to tst_u1;
openGauss=# SET ROLE tst_u1 PASSWORD 'tst_u1@123';
opengauss=> SET SEARCH_PATH TO tst_schema1;
openGauss=> show full columns from tst_t1;
Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment
-----------+------+-----------+------+-----+---------+-------+------------------+---------
addr | text | de_DE | YES | | NULL | | SELECT |
phone | text | es_ES | YES | | NULL | | SELECT |
意见反馈