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How can mixed data types (int, float, char, etc) be stored in an array?
...
You can make the array elements a discriminated union, aka tagged union.
struct {
enum { is_int, is_float, is_char } type;
union {
int ival;
float fval;
char cval;
} val;
} my_array[10];
The type member is used to hold the choice of w...
What are the options for storing hierarchical data in a relational database? [closed]
...lies? Perform a traversal on both sub-trees computing the intersection and union of the two sub-trees. The percent similar is the intersection divided by the union.
Transitive Closure: Walk the sub-tree and sum up the field(s) of interest, e.g. "How much aluminum is in a sub-assembly?"
Yes, you ca...
gem install: Failed to build gem native extension (can't find header files)
I am using Fedora 14 and I have MySQL and MySQL server 5.1.42 installed and running.
Now I tried to do this as root user:
1...
优惠券批量生成及导入的思路 - 闲聊区 - 清泛IT论坛，有思想、有深度
...个事实。假设我们可以随机生成不重复的整数，那么又该如何转换成上述”字母+数字”的混合字符串形势呢？答案是：36进制。36进制数的表达区间是0-9，A-Z(a-z)，恰好满足要求。因此，我的方法是用随机函数生成长整形并转换...
How to select only date from a DATETIME field in MySQL?
I have a table in the MySQL database that is set up with DATETIME . I need to SELECT in this table only by DATE and excluding the time.
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Python mysqldb: Library not loaded: libmysqlclient.18.dylib
I just compiled and installed mysqldb for python 2.7 on my mac os 10.6. I created a simple test file that imports
15 Answe...
Get the week start date and week end date from week number
...ple:
WITH TestData(SomeDate) AS (
SELECT CAST('20001225' AS DATETIME) UNION ALL
SELECT CAST('20001226' AS DATETIME) UNION ALL
SELECT CAST('20001227' AS DATETIME) UNION ALL
SELECT CAST('20001228' AS DATETIME) UNION ALL
SELECT CAST('20001229' AS DATETIME) UNION ALL
SELECT CAST...
Schrödingers MySQL table: exists, yet it does not
...or if you have backups, try the following:
Delete all schemas (excluding mysql)
shut down the database
Make sure that all folders in your data directory have been removed properly (again, excluding mysql)
delete ibdata and log files
restart the database. It should recreate the tablespace and logs ...
Why is '+' not understood by Python sets?
...ts don't have an implementation for the + operator.
You can use | for set union and & for set intersection.
Sets do implement - as set difference. You can also use ^ for symmetric set difference (i.e., it will return a new set with only the objects that appear in one set but do not appear in b...
Downloading MySQL dump from command line
...tion to a more noob-friendly service, I need to download the contents of a MySQL database. Is there a way I can do this from the command line?
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