INSERT INTO customers
VALUES (1, 'Babara', 'MacCaffrey', TO_DATE('1986-03-28', 'YYYY-MM-DD'), '781-932-9754', '0 Sage Terrace', 'Waltham', 'MA', 2273);
[42000][1950] ORA-01950: 对表空间 'USERS' 无权限 Position: 12
对于一个新建的用户，如果没有分配给unlimited table space系统权限的用户，必须先给他们指定限额，才能在表空间中创建对象。
SQL>ALTER USER 用户名 QUOTA UNLIMITED ON "USERS";
创建表时，其中一条语句编译报错
CONSTRAINT fk_orders_customers FOREIGN KEY (customer_id) REFERENCES customers (customer_id) ON update CASCADE
DELETE expected, got 'update'
Oracle本身只支持外键的级联删除，并不支持外键的级联更新。
我们可以通过触发器来实现外键的级联更新。如下：
create or replace trigger trg_orders_customer_id
after update
on customers
for each row
begin
if :NEW.customer_id <> :old.customer_id then
update orders set customer_id=:new.customer_id where customer_id = :old.customer_id;
end if;
end;
创建表时，其中一条语句编译报错
CONSTRAINT fk_client_id FOREIGN KEY (client_id) REFERENCES clients (client_id) ON DELETE RESTRICT
CASCADE or SET expected, got 'RESTRICT'
Oracle不支持使用这种方法来指定外键约束的删除行为。
我们可以通过触发器来实现。如下：
create or replace trigger trg_clients_invoices_id
before delete
on clients
for each row
declare
--变量声明，用于在触发器中存储查询结果的计数值
client_id_count NUMBER;
begin
select count(*)
INTO client_id_count
FROM invoices
WHERE client_id = :old.client_id;
if client_id_count > 0 then
raise_application_error(-20001, 'Cannot delete order. Related order items exist.');
end if;
end;
insert into CUSTOMERS (FIRST_NAME, LAST_NAME,BIRTH_DATE, ADDRESS, CITY, STATE)
values (
'John',
'Smith',
to_date('1990-01-01', 'YYYY-MM-DD'),
'address',
'city',
'CA');
[2023-12-13 23:05:00] [23000][1] ORA-00001: 违反唯一约束条件 (ORCL.PK_CUSTOMERS)
[2023-12-13 23:05:00] Position: 0
主键自增触发器所使用的序列从1开始。如下：
create sequence SEQ_CUSTOMERS
minvalue 1
nomaxvalue
start with 1
nocycle
cache 10;
创建表时，插入的初始数据没有通过触发器生成主键，因此序列还是从1开始。
插入的初始数据时使用代码如下：
INSERT INTO customers
VALUES (10, 'Levy', 'Mynett', TO_DATE('1969-10-13', 'YYYY-MM-DD'), '404-246-3370', '68 Lawn Avenue', 'Atlanta', 'GA', 796);
将序列删除，改成从11开始。如下：
drop sequence SEQ_CUSTOMERS;
create sequence SEQ_CUSTOMERS
minvalue 1
nomaxvalue
start with 11
nocycle
cache 10;
insert all
into SHIPPERS (NAME)
values ('shipper1')
into SHIPPERS (NAME)
values ('shipper2')
into SHIPPERS (NAME)
values ('shipper2')
select 1
from DUAL
[2023-12-14 21:51:07] [23000][1] ORA-00001: 违反唯一约束条件 (ORCL.PK_SHIPPERS)
[2023-12-14 21:51:07] Position: 0
该代码只会触发一次主键自增触发器，因此当多条数据插入时，会使用同一个被生成的主键。
一、通过联合（union）的方式批量插入，如下：
INSERT INTO shippers (name)
SELECT 'SHIPPER_1'
FROM dual
UNION
SELECT 'SHIPPER_2'
FROM dual
UNION
SELECT 'SHIPPER_3'
FROM dual;
二、插入时，声明主键，如下：
insert all
into SHIPPERS (shipper_id, NAME)
values (SHIPPERS_SEQ.nextval, 'shipper1')
into SHIPPERS (shipper_id,NAME)
values (SHIPPERS_SEQ.nextval+1,'shipper2')
into SHIPPERS (shipper_id,NAME)
values (SHIPPERS_SEQ.nextval+2,'shipper3')
select 1
from DUAL;
多表插入，插入ORDERS表后，获取自动生成的ORDER_ID值并插入ORDER_ITEMS表中。
begin
insert into ORDERS (ORDER_ID, customer_id, order_date, status)
values (SEQ_ORDERS.nextval, 1, to_date('1990-01-02', 'YYYY-MM-DD'), 1);
insert into ORDER_ITEMS
SELECT SEQ_ORDERS.currval, 1, 1, 2.95
from DUAL
union
SELECT SEQ_ORDERS.currval, 2, 1, 3.95
from DUAL;
end;
[2023-12-15 11:03:55] [65000][6550]
[2023-12-15 11:03:55] ORA-06550: 第 6 行, 第 23 列:
[2023-12-15 11:03:55] PL/SQL: ORA-02287: 此处不允许序号
[2023-12-15 11:03:55] ORA-06550: 第 5 行, 第 5 列:
[2023-12-15 11:03:55] PL/SQL: SQL Statement ignored
[2023-12-15 11:03:55] Position: 205
currval只能在SELECT语句中使用，并且必须在序列的NEXTVAL之后才能使用。在SELECT子句中直接使用SEQ_ORDERS.currval，这是不允许的。
将SEQ_ORDERS.currval的值存储在一个变量中，然后在SELECT子句中使用该变量。
DECLARE
new_order_id NUMBER;
begin
insert into ORDERS (ORDER_ID, customer_id, order_date, status)
values (SEQ_ORDERS.nextval, 1, to_date('1990-01-02', 'YYYY-MM-DD'), 1);
SELECT SEQ_ORDERS.currval INTO new_order_id FROM DUAL;
insert into ORDER_ITEMS
SELECT new_order_id, 1, 1, 2.95
from DUAL
union
SELECT new_order_id, 2, 1, 3.95
from DUAL;
end;
select c.CUSTOMER_ID, c.FIRST_NAME, c.LAST_NAME
from CUSTOMERS c
join ORDERS o using (customer_id)
join ORDER_ITEMS oi using (order_id)
where STATE = 'VA'
[2023-12-15 21:22:39] [99999][25154] ORA-25154: USING 子句的列部分不能有限定词
[2023-12-15 21:22:39] Position: 7
在Oracle中，USING子句用于指定两个表之间的列进行自动连接，但它不允许在列名中使用表限定词。
一、去掉表限定词，如下：
select CUSTOMER_ID, FIRST_NAME, LAST_NAME
from CUSTOMERS c
join ORDERS o using (customer_id)
join ORDER_ITEMS oi using (order_id)
where STATE = 'VA';
二、改为使用ON子句来指定连接条件，如下：
SELECT c.CUSTOMER_ID, c.FIRST_NAME, c.LAST_NAME
FROM CUSTOMERS c
JOIN ORDERS o ON c.customer_id= o.customer_id
JOIN ORDER_ITEMS oi ON o.order_id = oi.order_id
WHERE STATE = 'VA';
select INVOICE_ID,
INVOICE_TOTAL,
(select avg(INVOICE_TOTAL) from INVOICES) as invoice_average,
INVOICE_TOTAL - (select invoice_average)
from INVOICES
[2023-12-20 11:24:22] [42000][923] ORA-00923: 未找到要求的 FROM 关键字
[2023-12-20 11:24:22] Position: 159
Oracle中，在子查询中引用外部查询结果时，不能直接使用子查询的别名。
一、子查询嵌套到外部查询
SELECT INVOICE_ID,
INVOICE_TOTAL,
(SELECT AVG(INVOICE_TOTAL) FROM INVOICES) AS invoice_average,
INVOICE_TOTAL - (SELECT AVG(INVOICE_TOTAL) FROM INVOICES) AS difference
FROM INVOICES;
如果想避免重复执行同一个子查询可以通过内联视图。
二、内联视图
select t.INVOICE_ID,
t.INVOICE_TOTAL,
invoice_average,
t.INVOICE_TOTAL - invoice_average as difference
from INVOICES t, (select avg(INVOICE_TOTAL) as invoice_average from INVOICES);
注：内联视图只能用无相关子查询。
select concat(FIRST_NAME, ' ', FIRST_NAME) as full_name
from CUSTOMERS
[2023-12-21 10:15:10] [42000][909] ORA-00909: 参数个数无效
[2023-12-21 10:15:10] Position: 7
concat()函数默认只接受两个参数。
嵌套使用concat()函数
select concat(concat(FIRST_NAME, ' '), LAST_NAME) as full_name
from CUSTOMERS;
create view sales_by_client as
select c.CLIENT_ID,
c.NAME,
sum(INVOICE_TOTAL) as total_sales
from CLIENTS c
join INVOICES i on c.CLIENT_ID = i.CLIENT_ID
group by c.CLIENT_ID, c.NAME;
[2023-12-24 15:07:35] [42000][1031] ORA-01031: 权限不足
[2023-12-24 15:07:35] Position: 12
没有创建视图权限。
使用管理员账户登录到 Oracle 数据库，然后执行以下语句：
SQL> GRANT CREATE VIEW TO your_user;
create or replace procedure get_clients_by_state_default(p_state in varchar2)
is
client_record CLIENTS%rowtype;
begin
if p_state is null then
p_state := 'CA';
end if;
select * into client_record from CLIENTS c where c.STATE = p_state;
DBMS_OUTPUT.PUT_LINE(client_record.CLIENT_ID || ' ' || client_record.NAME);
end;
[2023-12-26 13:30:20] [99999][17110] Warning: 执行完毕, 但带有警告
[2023-12-26 13:30:20] completed in 1 s 882 ms
[2023-12-26 13:30:20] 6:9:PLS-00363: 表达式 'P_STATE' 不能用作赋值目标
[2023-12-26 13:30:20] 6:9:PL/SQL: Statement ignored
在 Oracle 中，存储过程的参数是只读的，不能直接对其进行赋值操作。
可以使用一个新的变量来接收默认值，并在存储过程中使用该变量进行查询。
create or replace procedure get_clients_by_state_default(p_state in varchar2)
is
client_record CLIENTS%rowtype;
v_state VARCHAR2(2); -- 新增变量用于接收默认值
begin
if p_state is null then
v_state := 'CA';
else
v_state := p_state;
end if;
select * into client_record from CLIENTS c where c.STATE = v_state;
DBMS_OUTPUT.PUT_LINE(client_record.CLIENT_ID || ' ' || client_record.NAME);
end;
设置当前会话的事务隔离级别
alter session set isolation_level = read committed;
[2023-12-30 14:58:40] [72000][1453] ORA-01453: SET TRANSACTION 必须是事务处理的第一个语句
[2023-12-30 14:58:40] Position: 0
SET TRANSACTION 语句必须在事务开始之前执行。
将之前的事务提交完，就可以执行该语句了。
commit;
alter session set isolation_level = read committed;
查看当前事务隔离级别：
--开启一个事务
select *
from DUAL for update;
--查看当前事务
SELECT s.sid,
s.serial#,
bitand(t.flag, POWER(2, 28)),
case bitand(t.flag, POWER(2, 28))
WHEN 0 THEN 'READ COMMITTED'
ELSE 'SERIALIZABLE'
END AS isolation_level
FROM v$transaction t
JOIN v$session s ON t.addr = s.taddr AND s.sid = sys_context('USERENV', 'SID');
[2023-12-30 14:30:05] [42000][942] ORA-00942: 表或视图不存在
[2023-12-30 14:30:05] Position: 212
没有查询v$transaction和v$session的权限。
GRANT SELECT ON V_$TRANSACTION TO your_user;
GRANT SELECT ON V_$SESSION TO your_user;