	一、用法

	  all:不考虑先后关系，只要满足条件，就全部插入；

	 first:考虑先后关系，如果有数据满足第一个when条件又满足第二个when条件，则执行第一个then插入语句，第二个then就不插入第一个then已经插入过的数据了。

	其区别也可描述为，all只要满足条件，可能会作重复插入；first首先要满足条件，然后筛选，不做重复插入。

	二、建表

	CREATE TABLE small_orders

	(order_id NUMBER(12) NOT NULL,

	customer_id NUMBER(6) NOT NULL,

	order_total NUMBER(8,2),

	sales_rep_id NUMBER(6)

)

	CREATE TABLE medium_orders AS SELECT * FROM small_orders;

	CREATE TABLE large_orders AS SELECT * FROM small_orders;
CREATE TABLE special_orders 
   (order_id       NUMBER(12)    NOT NULL,
    customer_id    NUMBER(6)     NOT NULL,
    order_total    NUMBER(8,2),
    sales_rep_id   NUMBER(6),
    credit_limit   NUMBER(9,2),
    cust_email     VARCHAR2(30)
   );

	三、用法案例

	(1)insert all-不带条件

	  insert all

	   into small_orders(order_id,customer_id,order_tall)

	       values (oid,cid,ottl)

	    into medium_orders(order_id,customer_id,sales_rep_id)

	      values (oid,cid,sid)

	SELECT o.order_id oid, o.customer_id cid, o.order_total ottl,
    o.sales_rep_id sid, c.credit_limit cl, c.cust_email cem
      FROM orders o, customers c
      WHERE o.customer_id = c.customer_id;

	(2)insert all 带条件

	INSERT ALL
    WHEN order_total < 1000000 THEN
        INTO small_orders
   WHEN order_total > 1000000 AND order_total < 2000000 THEN
        INTO medium_orders
   WHEN order_total > 2000000 THEN
        INTO large_orders
  SELECT order_id, order_total, sales_rep_id, customer_id  FROM orders;

	INSERT ALL

	WHEN ottl < 100000 THEN

	INTO small_orders
         VALUES(oid, ottl, sid, cid)
   WHEN ottl > 100000 and ottl < 200000 THEN
      INTO medium_orders 
         VALUES(oid, ottl, sid, cid)
   WHEN ottl > 200000 THEN
      into large_orders
         VALUES(oid, ottl, sid, cid)
   WHEN ottl > 290000 THEN
      INTO special_orders
   SELECT o.order_id oid, o.customer_id cid, o.order_total ottl,
      o.sales_rep_id sid, c.credit_limit cl, c.cust_email cem
      FROM orders o, customers c
      WHERE o.customer_id = c.customer_id;
（3）insert first

insert all 和insert first多表插入用法