Tag：count
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Time：2021-7-1
General query db.User.Select(u => u); // Query without condition db.User.Where(u => true); // Query without condition db.User.Where(u => u.username == “wjl” || u.username == “hyf”); // Conditional query ||| means “or” & & means “and” DB. User. Select (U = > U. username. Endswith (“Li”))// Fuzzy query is equivalent to like ‘%’ DB. User. Select […]
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Time：2021-6-18
Reading notes of objc runtime source code (1) My blogMax’s BlogThe source code of this article comes fromapple opensource。 1.objc-private.h Open the header file to see two familiar structure pointers typedef struct objc_class *Class; typedef struct objc_object *id; We use it a lotidThis pointer is olderFoundationFramework, the general initialization method will return aidObject, and some […]
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Time：2021-6-17
Example 1: Using the feature that the channel pop will automatically suspend the current coroutine and wait for the producer to push the data, the concurrent call is realized, and the result set is combined after the coroutine is completed. $serv = new Swoole\Http\Server(“127.0.0.1”, 9503, SWOOLE_BASE); $serv->on(‘request’, function ($req, $resp) { $chan = new Swoole\Coroutine\Channel(2); […]
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Time：2021-5-10
In SQL server, count (*) or count (1) or count ([column]) is probably the most commonly used aggregate function. In fact, many people can’t distinguish the three. This article will elaborate the function, relationship and the underlying principle of the three. Usually, I often see some so-called optimization suggestions that use count (1) instead of […]
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Time：2021-5-6
Interview 10 companies, get 9 offers, PHP interview questions in 2020 PS: This article includes selected interview questions and knowledge. PHP interview questions about PHP’s garbage collection mechanism. PHP’s garbage collection mechanism refers to GC mechanism. PHP can automatically manage memory and clear unnecessary objects. PHP interview questions share PHP’s interview questions about garbage collection […]
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Time：2021-5-5
1、 Operator 1. Arithmetic operator Arithmetic operator + – * / % ++ — Comparison operator > >= < <= != == === !== be careful: ————————————————- In the assignment operation: I + + means to first give the value of I to the left variable, and then add I on this basis++ ++I stands […]
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Time：2021-5-3
This article is wrong and has no reference value This article is wrong and has no reference value This article is wrong and has no reference value This article is wrong and has no reference value This article is wrong and has no reference value I was interested in this topic a few days ago, […]
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Time：2021-4-21
This article is updated on June 14, 2020, using MySQL 5.7 and operating system deepin 15.4. catalog Arithmetic operator Comparison operator Logical operators Bitwise Operators Operator priority Arithmetic operator operator grammar explain + a + b addition – a – b subtraction * a * b multiplication / a / b Division. similarDIV, butDIVThe results […]
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Time：2021-4-21
In SQL server, count (*) or count (1) or count ([column]) is probably the most commonly used aggregate function. In fact, many people can’t distinguish the three. This article will elaborate the function, relationship and the underlying principle of the three. Usually, I often see some so-called optimization suggestions that use count (1) instead of […]
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Time：2021-4-18
state In Flink, fault tolerance, state consistency and checkpoint mechanism are realized by state, Generally speaking, the state is to back up the data or the intermediate results of program operation, which can ensure that the program can recover from the midway error; State type What are the specific types of saved states in the […]
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Time：2021-3-31
Interview questions: selected topics. PHP interview questions about PHP’s garbage collection mechanism. PHP’s garbage collection mechanism refers to GC mechanism. PHP can automatically manage memory and clear unnecessary objects. PHP interview questions share PHP’s interview questions about garbage collection mechanism My PHP learning and communication community-1023755567. Group management is ready, bat and other advanced knowledge […]
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Time：2021-3-29
Kernel object is a relatively difficult concept to understand. The root of the problem lies in that even in the book core programming, it does not clearly define it, but constantly illustrates and describes its properties and how to use it. A blind man can’t see the whole picture.We can only enumerate its properties as […]
