数据库中的不同类型

----一共有多少种数据类型
select distinct data_type from user_tab_cols;

LONG
NVARCHAR2
TIMESTAMP(6)
FLOAT
NUMBER
CHAR
CLOB
UROWID
NCHAR
DATE
RAW
VARCHAR2
BLOB

----系统种涉及的类型的有哪些表，当然还有些数据类型并没有纳入进来。我们以后将其加入。
select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='LONG';
select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='NUMBER';
select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='FLOAT';

select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='DATE';
select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='TIMESTAMP(6)';

select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='CHAR';
select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='NCHAR';
select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='VARCHAR2';
select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='NVARCHAR2';
select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='CLOB';

select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='UROWID';

select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='RAW';
select t.TABLE_NAME,t.COLUMN_NAME,t.DATA_TYPE,t.DATA_LENGTH,t.DATA_PRECISION,t.DATA_SCALE,t.LOW_VALUE,t.HIGH_VALUE from user_tab_cols t  where  t.DATA_TYPE='BLOB';