整理这篇Oracle基本语法FAQ最初是为了回答一位客户朋友的提问（客观情况所限，我无法在线回答问题）。这些解答并非唯一答案，只是答案之一。更完备的答案请查阅Oracle正式文档。
A. CREATE TABLE ROYAL_MTABLE
(
RM_INT_FIELD INTEGER,
RM_STR_FIELD VARCHAR2(64)
)
CREATE TABLE ROYAL_DTABLE
(
RD_INT_FIELD INTEGER,
RD_STR_FIELD VARCHAR2(32)
)
A. DROP TABLE ROYAL_DTABLE;
A. CREATE OR REPLACE VIEW ROYAL_MDVIEW AS
SELECT T1.RM_STR_FIELD AS F1, T2.RD_STR_FIELD AS F2 FROM ROYAL_MTABLE T1, ROYAL_DTABLE T2
WHERE T1.RM_INT_FIELD = T2.RM_INT_FIELD
A. DROP VIEW ROYAL_MDVIEW;
A. ALTER TABLE ROYAL_DTABLE ADD RM_INT_FIELD INTEGER;
A. ALTER TABLE ROYAL_DTABLE DROP COLUMN RM_INT_FIELD;
A. ALTER TABLE ROYAL_MTABLE MODIFY RM_STR_FIELD NOT NULL;
A. ALTER TABLE ROYAL_MTABLE MODIFY RM_STR_FIELD NULL;
A. ALTER TABLE ROYAL_MTABLE ADD CONSTRAINT PK_ROYAL_MTABLE PRIMARY KEY (RM_INT_FIELD);
A. ALTER TABLE ROYAL_MTABLE DROP CONSTRAINT PK_ROYAL_MTABLE CASCADE;
A. ALTER TABLE ROYAL_DTABLE ADD CONSTRAINT FK_ROYAL_DTABLE FOREIGN KEY (RM_INT_FIELD) REFERENCES ROYAL_MTABLE (RM_INT_FIELD) ON DELETE CASCADE;
A. ALTER TABLE ROYAL_DTABLE DROP CONSTRAINT FK_ROYAL_DTABLE;
A. ALTER TABLE ROYAL_MTABLE ADD CONSTRAINT CHK_RM_STR_FIELD CHECK (RM_STR_FIELD IN ('Y','N'));
A. ALTER TABLE ROYAL_MTABLE DROP CONSTRAINT CHK_RM_STR_FIELD;
A. ALTER TABLE ROYAL_DTABLE MODIFY RD_STR_FIELD DEFAULT 'ROYAL';
A. ALTER TABLE ROYAL_DTABLE MODIFY RD_STR_FIELD DEFAULT NULL;
A. CREATE UNIQUE INDEX IDX_ROYAL_DTABLE ON ROYAL_DTABLE (RM_INT_FIELD);
A. DROP INDEX IDX_ROYAL_DTABLE;
A. CREATE USER TESTUSER IDENTIFIED EXTERNALLY DEFAULT TABLESPACE USERS TEMPORARY TABLESPACE TEMP PROFILE DEFAULT;
A. DROP USER TESTUSER CASCADE;
Q21.怎样将对象权限（object privileges）授予用户？
A. GRANT SELECT, INSERT, UPDATE, DELETE, ALTER ON ROYAL_MTABLE TO TESTUSER;
GRANT INSERT, UPDATE, DELETE ON ROYAL_DTABLE TO TESTUSER;
GRANT SELECT, ALTER ON ROYAL_DTABLE TO TESTUSER WITH GRANT OPTION;
A. REVOKE SELECT, INSERT, UPDATE, DELETE, ALTER ON ROYAL_DTABLE FROM TESTUSER;
Q23.怎样将角色权限（role privileges）授予用户？
A. GRANT CONNECT TO TESTUSER WITH ADMIN OPTION;
GRANT DBA TO TESTUSER;
A. REVOKE DBA FROM TESTUSER;
Q25.怎样将系统权限（system privileges）授予用户？
A. GRANT ALTER ANY TABLE TO TESTUSER WITH ADMIN OPTION;
A. REVOKE ALTER ANY TABLE FROM TESTUSER;
A. CREATE SEQUENCE RM_INT_FIELD_SEQ
MINVALUE 1
MAXVALUE 999999999999999999999999999
START WITH 1
INCREMENT BY 1
CACHE 10
ORDER;
A. DROP SEQUENCE RM_INT_FIELD_SEQ;
A. SELECT RM_INT_FIELD_SEQ.NEXTVAL FROM DUAL;
A. CREATE ROLE TESTROLE;
A. DROP ROLE TESTROLE;
Q32.怎样将对象权限（object privileges）授予角色？
A. GRANT SELECT, INSERT, UPDATE, DELETE, ALTER ON ROYAL_MTABLE TO TESTROLE;
A. REVOKE SELECT, INSERT, UPDATE, DELETE, ALTER ON ROYAL_MTABLE FROM TESTROLE;
Q34.怎样将角色权限（role privileges）授予角色？
A. GRANT DBA TO TESTROLE;
A. REVOKE DBA FROM TESTROLE;
Q36.怎样将系统权限（system privileges）授予角色？
A. GRANT CREATE TABLE TO TESTROLE;
A. REVOKE CREATE TABLE FROM TESTROLE;
Q38.不等于条件有哪几种写法？（茴香豆问题:)）
A. SELECT * FROM ROYAL_MTABLE WHERE RM_STR_FIELD != 'Y';
SELECT * FROM ROYAL_MTABLE WHERE RM_STR_FIELD ^= 'Y';
SELECT * FROM ROYAL_MTABLE WHERE RM_STR_FIELD <> 'Y';
A. SELECT * FROM ROYAL_DTABLE WHERE RD_STR_FIELD LIKE '%Y%';
SELECT * FROM ROYAL_DTABLE WHERE RD_STR_FIELD LIKE '_Y%';
A. SELECT * FROM ROYAL_DTABLE WHERE RM_INT_FIELD IN (SELECT RM_INT_FIELD FROM ROYAL_MTABLE WHERE RM_STR_FIELD NOT IN ('Y','B'));
A. || 连接两个字符串； LENGTH 字符串长度； TRIM/LTRIM/RTRIM 截断串左（右）指定字符串（包括空串）； LOWER/UPPER 将字符串转换为小/大写，等等。
例如：SELECT RM_INT_FIELD||'--'||RM_STR_FIELD||'YES' FROM ROYAL_MTABLE;
A. Oracle支持所有常用数字函数，包括（但不限于）+、-、*、/、ABS、COS、EXP、LN、LOG、MOD、POWER、ROUND、SIN、SINH、SQRT、TAN、TRUNC、AVG、COUNT、MAX、MIN、SUM、GREATEST、LEAST等等。
例如：
SELECT GREATEST(3, 4, 5)*4 FROM DUAL;
SELECT POWER(2,3) FROM DUAL;
A. SELECT SYSDATE FROM DUAL;
SELECT TO_CHAR(SYSDATE, 'YYYY-MM-DD HH:MI:SS') FROM DUAL;
A. SELECT TO_DATE('2002-11-27', 'YYYY-MM-DD') FROM DUAL;
SELECT TO_DATE('2002-11-27 09:28:55', 'YYYY-MM-DD HH:MI:SS') FROM DUAL;
A. NEXT_DAY LAST_DAY ADD_MONTHS MONTHS_BETWEEN等等。
例如：SELECT LAST_DAY(SYSDATE) FROM DUAL;
A. DECODE函数的格式为DECODE(value, if1, then1, if2, then2...,else)。假设表ROYAL_DTABLE中有如下数据：
RD_INT_FIELD RD_STR_FIELD RM_INT_FIELD
--------------------------------------
1 royal 1
2 bill 2
3 joy 1
请观察如下SQL语句输出结果。
SELECT DECODE(RD_STR_FIELD, 'royal', 'royaltest', 'bill', 'billgates', RD_STR_FIELD) AS DC FROM ROYAL_DTABLE;
DC
---------
royaltest
billgates
joy
Q47.能给出一个group by、having和order by用法的例子吗？
A. SQL> SELECT * FROM ROYAL_MTABLE;
RM_INT_FIELD RM_STR_FIELD
-------------------------
1 Y
2 N
3 Y
SQL> SELECT * FROM ROYAL_DTABLE;
RD_INT_FIELD RD_STR_FIELD RM_INT_FIELD
--------------------------------------
1 royal 1
2 bill 2
3 joy 1
SQL> SELECT RM_INT_FIELD, SUM(RD_INT_FIELD) FROM ROYAL_DTABLE GROUP BY RM_INT_FIELD HAVING SUM(RD_INT_FIELD) >= 2 ORDER BY SUM(RD_INT_FIELD) ASC;
RM_INT_FIELD SUM(RD_INT_FIELD)
------------------------------
2 2
1 4
A. USER_TABLES(TABS)、USER_TAB_COLUMNS(COLS)、USER_VIEWS、USER_SEQUENCES(SEQ)、USER_CONSTRAINTS、USER_CONS_COLUMNS、USER_TAB_COMMENTS、USER_COL_COMMENTS、USER_INDEXES(IND)、USER_IND_COLUMNS、USER_USERS、DBA_USERS、ALL_USERS、USER_TABLESPACES等等。
例如：SELECT * FROM USER_CONSTRAINTS WHERE CONSTRAINT_NAME = 'FK_ROYAL_DTABLE';
A. INSERT INTO ROYAL_MTABLE (RM_INT_FIELD, RM_STR_FIELD, RM_DATE_FIELD) VALUES (9, 'Y', TO_DATE('2002-05-23', 'YYYY-MM-DD'));
INSERT INTO ROYAL_MTABLE (RM_INT_FIELD, RM_STR_FIELD, RM_DATE_FIELD) VALUES (10, 'Y', TO_DATE('2002-10-10 8:23:33', 'YYYY-MM-DD HH:MI:SS'));
A. connect by子句提供了遍历“树”的手段。
假设有这样一个表：CREATE TABLE ROYAL_TREETABLE (ID INTEGER, PARENT_ID INTEGER, NAME VARCHAR2(32));
表中有如下数据：
ID PARENT_ID NAME
-----------------
2 1 AAA
3 1 BBB
4 2 CCC
5 2 DDD
6 4 EEE
8 7 GGG
假如我们现在需要从NAME = 'EEE'的记录开始，向上查找所有有父子关系的记录，可执行如下SQL语句：
SELECT * FROM ROYAL_TREETABLE START WITH NAME = 'EEE' CONNECT BY ID = PRIOR PARENT_ID;
ID PARENT_ID NAME
-----------------
6 4 EEE
4 2 CCC
2 1 AAA
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