union

问题 I have a PHP function that returns me an array with category information. It is supposed to be provided with a $categoryId, and then return that category and any category "above" it. This is working: Table structure of tbl_categories : CREATE TABLE `tbl_categories` ( `categoryId` int(11) NOT NULL, `categoryParentId` int(11) NOT NULL, `categoryName` varchar(50) NOT NULL, `categoryDescr` varchar(400) NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8; ALTER TABLE `tbl_categories` ADD PRIMARY KEY (

问题 I have a PHP function that returns me an array with category information. It is supposed to be provided with a $categoryId, and then return that category and any category "above" it. This is working: Table structure of tbl_categories : CREATE TABLE `tbl_categories` ( `categoryId` int(11) NOT NULL, `categoryParentId` int(11) NOT NULL, `categoryName` varchar(50) NOT NULL, `categoryDescr` varchar(400) NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8; ALTER TABLE `tbl_categories` ADD PRIMARY KEY (

问题 This topic is related to my previews one Join two tables with all records I'm tryng now to join 3 or more tables in my Laravel controller code, and view them in one Datatable. table1 +--------------------+---------+ | recordtime | tempout | +--------------------+---------+ | 4.12.2020 10:00:00 | 1.1 | | 4.12.2020 10:30:00 | 1.2 | | 4.12.2020 11:00:00 | 1.3 | | 4.12.2020 11:30:00 | 1.4 | | 4.12.2020 12:00:00 | 1.5 | +--------------------+---------+ table2 +--------------------+---------+ |

问题 Say I'm having a following code in C union u_type { uint32_t data; uint8_t chunk[4]; } 32bitsdata; 32bitsdata.chunk[0] = some number; 32bitsdata.chunk[1] = some number; 32bitsdata.chunk[2] = some number; 32bitsdata.chunk[3] = some number; printf("Data in 32 bits: %d\n", 32bitsdata.data); How could I do similar thing in python? I'm trying to read a binary file (byte by byte) - already got it working, and combining every 3 bytes into one int. Heard struct would do the trick, but I'm not really

问题 Say I'm having a following code in C union u_type { uint32_t data; uint8_t chunk[4]; } 32bitsdata; 32bitsdata.chunk[0] = some number; 32bitsdata.chunk[1] = some number; 32bitsdata.chunk[2] = some number; 32bitsdata.chunk[3] = some number; printf("Data in 32 bits: %d\n", 32bitsdata.data); How could I do similar thing in python? I'm trying to read a binary file (byte by byte) - already got it working, and combining every 3 bytes into one int. Heard struct would do the trick, but I'm not really

问题 Say I'm having a following code in C union u_type { uint32_t data; uint8_t chunk[4]; } 32bitsdata; 32bitsdata.chunk[0] = some number; 32bitsdata.chunk[1] = some number; 32bitsdata.chunk[2] = some number; 32bitsdata.chunk[3] = some number; printf("Data in 32 bits: %d\n", 32bitsdata.data); How could I do similar thing in python? I'm trying to read a binary file (byte by byte) - already got it working, and combining every 3 bytes into one int. Heard struct would do the trick, but I'm not really

问题 Let's say I want to have the following bitfield: struct SortingKey { uint8_t a: 2; uint8_t b: 4; uint8_t c: 2; } To use a simple integer comparison, I may need to wrap it into an union like this and use value for sorting: union UnionSortKey { SortingKey key; uint8_t value; } However, in C++, reading an inactive union member is Undefined Behaviour. How can I guarantee that I do not fall into UB but keeping a simple integer comparison? 回答1: You can't use union for type punning, In C++20, you

来源： https://stackoverflow.com/questions/63200469/how-to-sort-this-mysql-query

来源： https://stackoverflow.com/questions/15370394/are-these-two-relations-compatible-for-a-union-operation

来源： https://stackoverflow.com/questions/15370394/are-these-two-relations-compatible-for-a-union-operation