1.只查看某个特定表的字段名

SELECT column_name, data_type, data_length
FROM user_tab_columns
WHERE table_name = '你的表名' -- 注意大写
ORDER BY column_id;

2.查看当前用户下所有表的字段名

SELECT table_name, column_name, data_type, data_length
FROM user_tab_columns
ORDER BY table_name, column_id;

说明：
table_name: 表名
column_name: 字段名
data_type: 数据类型（如 VARCHAR2, NUMBER）
data_length: 数据长度

若需要格式化字段展示，可使用如下SQL：

SELECT table_name || '.' || column_name AS full_column_name,data_type || '(' || data_length || ')' AS data_type_length
FROM user_tab_columns
ORDER BY table_name, column_id;

3.查看所有用户的表字段名（你有权限访问的）

SELECT owner, table_name, column_name, data_type, data_length
FROM all_tab_columns
ORDER BY owner, table_name, column_id;

4.查看数据库中所有表的字段名（需要 DBA 权限）

SELECT owner, table_name, column_name, data_type, data_length
FROM dba_tab_columns
ORDER BY owner, table_name, column_id;

5.查看当前用户下字段名、数据类型及长度

SELECT table_name,column_name,-- 格式化数据类型 + 长度/精度CASE WHEN data_type IN ('CHAR', 'VARCHAR2', 'NCHAR', 'NVARCHAR2') THEN data_type || '(' || CASE char_used WHEN 'C' THEN char_length || ' CHAR'WHEN 'B' THEN data_length || ' BYTE'END || ')'WHEN data_type = 'NUMBER' THEN CASE WHEN data_precision IS NULL THEN 'NUMBER' WHEN data_scale = 0 THEN 'NUMBER(' || data_precision || ')' ELSE 'NUMBER(' || data_precision || ',' || data_scale || ')'ENDELSE data_typeEND AS formatted_data_type,-- 实际存储长度（以字节为单位）data_length AS actual_length_bytesFROM user_tab_columns
ORDER BY table_name, column_id;

若需格式化显示字段长度，可使用如下SQL:

SELECT table_name,column_name,-- 格式化数据类型（去掉 BYTE/CHAR）CASE WHEN data_type IN ('CHAR', 'VARCHAR2', 'NCHAR', 'NVARCHAR2') THEN data_type || '(' || CASE char_used WHEN 'C' THEN char_lengthWHEN 'B' THEN data_lengthEND || ')'WHEN data_type = 'NUMBER' THEN CASE WHEN data_precision IS NULL THEN 'NUMBER' WHEN data_scale = 0 THEN 'NUMBER(' || data_precision || ')' ELSE 'NUMBER(' || data_precision || ',' || data_scale || ')'ENDELSE data_typeEND AS formatted_data_type,-- 实际字节长度（定义层面上的）data_length AS actual_length_bytesFROM user_tab_columns
ORDER BY table_name, column_id;

6.查询前用户下所有表的字段名称、字段长度、是否允许为空

SELECT table_name,column_name,data_type,CASE WHEN data_type IN ('CHAR', 'VARCHAR2', 'NCHAR', 'NVARCHAR2') THENchar_lengthWHEN data_type = 'NUMBER' THENdata_precisionELSEdata_lengthEND AS length,CASE WHEN nullable = 'Y' THEN '是'ELSE '否'END AS is_nullable
FROM user_tab_columns
ORDER BY table_name, column_id;

若需格式化显示长度，可使用如下SQL:

SELECT table_name,column_name,CASE WHEN data_type IN ('CHAR', 'VARCHAR2', 'NCHAR', 'NVARCHAR2') THEN data_type || '(' || CASE char_used WHEN 'C' THEN char_length WHEN 'B' THEN data_length ELSE data_length END || ')'WHEN data_type = 'NUMBER' THEN CASE WHEN data_precision IS NULL THEN 'NUMBER'WHEN data_scale = 0 THEN 'NUMBER(' || data_precision || ')'ELSE 'NUMBER(' || data_precision || ',' || data_scale || ')'ENDELSE data_typeEND AS data_type_length,CASE WHEN nullable = 'Y' THEN '是'ELSE '否'END AS is_nullable
FROM user_tab_columns
ORDER BY table_name, column_id;