：SQL查询一张表的全部字段名称、类型、长度

Oracle数据库：

SELECT column_name, data_type, data_length 
FROM all_tab_columns 
WHERE table_name = 'YOUR_TABLE_NAME'
ORDER BY column_id;

MySQL/MariaDB数据库：

SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH 
FROM INFORMATION_SCHEMA.COLUMNS 
WHERE TABLE_SCHEMA = 'YOUR_DATABASE_NAME'
AND TABLE_NAME = 'YOUR_TABLE_NAME';

SQL Server数据库：

SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH 
FROM INFORMATION_SCHEMA.COLUMNS 
WHERE TABLE_NAME = 'YOUR_TABLE_NAME';

PostgreSQL数据库：

SELECT column_name, data_type, character_maximum_length 
FROM information_schema.columns 
WHERE table_name = 'your_table_name';

DM(达梦)数据库：

SELECT atc.COLUMN_NAME, atc.DATA_TYPE, atc.DATA_LENGTH 
FROM ALL_TAB_COLUMNS atc 
WHERE atc.TABLE_NAME = 'YOUR_TABLE_NAME';

​