更新日期：2024年09月11日
ifx_cl_card() 函数返回指定的集合类型主变量的基数。
语法
mint ifx_cl_card(collp, isnull)
ifx_collection_t *collp;
mint *isnull;
collp
指向应用程序中 collection 主变量的名称的指针。
isnull
如果该集合为空，则设置为 1，否则，设置为 0
用法
ifx_cl_card() 函数使得您能够确定集合中元素的数目、是否为空集合，以及集合是否
为空值。
返回代码
0
空集合。
>0
集合中元素的数目。
<0
发生错误。
示例
GBase 8s ESQL/C 编程指南
南大通用数据技术股份有限公司
- 699 -
此样例程序在 demo 目录中的 ifx_cl_card.ec 文件中。
/*
* Check the cardinality of the collection variable when
* the data is returned from the server
*/
main()
{
exec sql begin declare section;
client collection myset;
exec sql end declare section;
mint numelems = 0;
mint isnull = 0;
exec sql allocate collection ::myset;
exec sql create database newdb;
exec sql create table tab (col set(int not null));
exec sql insert into tab values ("set{}");
exec sql select * into :myset from tab;
if ((ifx_cl_card(myset, &isnull) == 0) && isnull == 0)
printf("collection is empty\n");
else if ((ifx_cl_card(myset, &isnull) == 0) && isnull == 1)
printf("collection is null\n");
else if ((numelems = ifx_cl_card(myset, &isnull))> 0)
printf("number of elements is %d\n", numelems);
else
printf("error occurred\n");
exec sql update tab set col = ’set{1,2,3}’;
exec sql select * into :myset from tab;
if ((ifx_cl_card(myset, &isnull) == 0) && isnull == 0)
printf("collection is empty\n");
GBase 8s ESQL/C 编程指南
南大通用数据技术股份有限公司
- 700 -
else if ((ifx_cl_card(myset, &isnull) == 0) && isnull == 1)
printf("collection is null\n");
else if ((numelems = ifx_cl_card(myset, &isnull))> 0)
printf("number of elements is %d\n", numelems);
else
printf("error occurred\n");
exec sql update tab set col = NULL;
exec sql select * into :myset from tab;
if ((ifx_cl_card(myset, &isnull) == 0) && isnull == 0)
printf("collection is empty\n");
else if ((ifx_cl_card(myset, &isnull) == 0) && isnull == 1)
printf("collection is null\n");
else if ((numelems = ifx_cl_card(myset, &isnull))> 0)
printf("number of elements is %d\n", numelems);
else
printf("error occurred\n");
}
输出
collection is empty
number of elements is 3
collection is null