小编Jef*_*emp的帖子

我创建了一个链表.一切正常.

我只是想知道我的代码是否有任何潜在危险.我关注的代码片段是我的推送,弹出和清理.代码的各个部分仅供用户交互,因此不是很重要(无论如何我都发布了,以便我在做什么时更清楚).只是链表应用程序.

非常感谢任何建议,因为这是我的第一次尝试.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct product_data product_data_t;
struct product_data
{
    int product_code;
    char product_name[128];
    int product_cost;
    product_data_t *next;
};

static product_data_t *head = NULL;
static product_data_t *tail = NULL;
static product_data_t *new_product = NULL;

// Push a product on to the list.
void push(int code, char name[], int cost); 
// Pop (delete) a product from the list.
void pop(int code);
// Display all product in the list.
void display_list();
// Delete all memory allocated …

由此:

Hotel                     Type   Room Guest                                     From      To
    ------------------------- ------ ---- ----------------------------------------- --------- ---------
    University Inn & Suites   Double 101  George Brown                              11-SEP-10 14-SEP-10
    University Inn & Suites   Double 101  George Brown                              11-OCT-10 13-OCT-10
    University Inn & Suites   Double 102
    University Inn & Suites   Double 103
    University Inn & Suites   Double 104
    University Inn & Suites   Double 105
    University Inn & Suites   Family 106  George Brooks                             22-SEP-10 27-SEP-10
    University Inn & Suites   Family 107
    University Inn & Suites   Single 201  Sandra …

当我想在oracle中看到一个带有其记录的表时,表是杂乱无章的,我的意思是不像my-sql在属性名称下看到属性的每个值!我该如何解决？

这是oracle 10g.如果我从sqlplus发出一个表的更新但是没有提交,那么在另一个会话中更新同一行并尝试提交,它只会挂起,直到我提交第一个.我知道有些人认为它是锁定机制,但我们的应用程序做了同样的事情,用户被阻止了.

什么是避免这个问题的最佳方法？

SELECT
/*+ INDEX(ID_BL_REF_NO REF_number_BL_idx*/ DECODE(BL_TYPE,'E',BL_ORIGIN_NAME,'I',BL_FINAL_NAME) FROM_PORT,
 DECODE(BL_TYPE,'I',BL_ORIGIN_NAME,'E',BL_FINAL_NAME) TO_PORT,
(BL_VESSEL_CONNECT||'/'||BL_VOYAGE_CONNECT||'/'||BL_PORT_CONNECT) Mother_vessel_voyage_port,
SUM(BLC_SIZE) No_of_20s,
SUM(BLC_SIZE)  No_of_40s,
SUM(DECODE(BLC_SIZE,'20',1,'40',2)) Teus,
SUM(BLC_GROSSWT) GrossWt,
round((BLC_GROSSWT/SUM(DECODE(BLC_SIZE,'20',1,'40',2))),2) AverageWt,
SUM(DECODE(BLF_MODE,'P',BLF_LOCAL_AMOUNT)) PREPAID,
SUM(DECODE(BLF_MODE,'C',BLF_LOCAL_AMOUNT)) COLLECT,
SUM(DECODE(BLF_MODE,'E',BLF_LOCAL_AMOUNT)) ELSEWHERE,
(SUM(DECODE(BLF_MODE,'P',BLF_LOCAL_AMOUNT)+DECODE(BLF_MODE,'C',BLF_LOCAL_AMOUNT)+DECODE(BLF_MODE,'E',BLF_LOCAL_AMOUNT))/SUM(DECODE(BLC_SIZE,'20',1,'40',2))) AVERAGE
FROM ID_BL_DETAILS,id_bl_containers,ID_BL_FREIGHT
WHERE BL_REFNO=BLC_REFNO
AND BLF_REFNO=BLC_REFNO
GROUP BY BL_VESSEL_CONNECT,BL_VOYAGE_CONNECT,BL_PORT_CONNECT,BL_ORIGIN_NAME,BL_LODPORT,BL_DISPORT,BL_FINAL_NAME,BLC_GROSSWT,BL_TYPE

我通过Application Express使用Oracle 10g XE版本,并使用-字符显示NULL .我从参数列表中发现:

+-------+-------+------------+--------------------------------------------+
| Name  | Value | Is Default |                Description                 |
+-------+-------+------------+--------------------------------------------+
| event | -     | TRUE       | debug event control - default null string  |
+-------+-------+------------+--------------------------------------------+

有没有办法更改此值,以便显示NULL NULL而不是-？

如果以前创建了一个表,我需要在我的数据库上运行一个delete语句.

问题是 - 我不能只运行delete语句,因为产品不在每个客户端的生产环境中 - 因此,他们没有我想要运行delete语句的表,并且最终会出现错误00942. 00000 - "table or view does not exist".

一个例子:

我想运行这样的东西:

IF EXISTS (TABLE TB_FIELD)
    DELETE FROM TB_FIELD WHERE ID = '213';

如果没有通用语句,我想要一个可以运行Oracle数据库的语句

我有2张桌子:

Table A:      TableB:
ID            ID    Value
1             2     0.5
2             3     10
3

我的查询:

SELECT A.ID,B.VALUE FROM A LEFT JOIN B ON A.ID = B.ID;

结果:

ID    Value
1      
2     0.5
3     10

我想用' - '替换null值,我尝试使用NVL(B.VALUE,' - '),但这不起作用,所以我该怎么办？