How to use conditional query? Summary of conditional query example usage

This article mainly introduces the MVC cross-database multi-table joint dynamic condition query function implemented by asp.net. It analyzes in detail the cross-database multi-table joint query function implementation skills of asp.net based on the MVC architecture in the form of examples. It needs Friends can refer to the following example of this article which describes the MVC cross-database multi-table joint dynamic condition query function implemented by asp.net. Share it with everyone for your reference, the details are as follows: 1. Method in the controller [HttpGet] public ActionResult Search() { ViewBag.HeadTitle = "Search"; ViewBag.MetaKey = "\"123\""; ViewBag.MetaDes = "\"456\&qu

1. asp.net cross-database multi-table joint dynamic condition query code example

Introduction: This article mainly introduces the MVC cross-database multi-table joint dynamic condition query function implemented by asp.net, and analyzes asp in detail in the form of examples. .net cross-database multi-table joint query function implementation skills based on MVC architecture, friends in need can refer to

2. Mysql common basic operation syntax (6)--Yes Conditional query for sorting data and limiting the number of results [command line mode]

##Introduction: 1. Use order by sorts the query results in asc ascending order and desc descending order: You can also specify multiple field names and sorting methods after order by for multi-level sorting: 2. Use limit to limit the number of query results: 0 in the above figure represents the query The starting position can also be understood as the number to skip; 2 in the above figure represents the number that needs to be queried. There are 3 pieces of data in this table. Because the number of pieces is limited to 2, the actual result is only two. In addition, the initial position here is 0. In fact, you don’t need to write it. The default is 0: There is another situation here, which is

3. Mysql common basic operation syntax (five )--Simple conditional query on data [command line mode]

Introduction: 1. Single condition Query: select field name from tablename where condition; 2. Simple multi-condition query, use && or between and, etc.: 3. is null and is not null query, pay attention here that null is not an empty string and is not 0: 4. in and not In query is equivalent to using or to connect the set elements behind in. Note that if there is null in the collection after in, it will not affect the result, but if there is null in the collection after not in, it will not

4. Mysql common basic operations Syntax (4) - Simple unconditional query of data and database and table query [command line mode]

Introduction: 1. Mysql simple query: select field 1, field 2... from tablename; If you write a * in the field, it means querying all fields, which is equivalent to specifying all field names, so if you want to query all Field data is generally represented by *. 2. Deduplication query: select distinct field 1, field 2... form tablename; it can be compared with the results of the previous picture. 3. Perform the four mathematical operations directly during the query, including addition, subtraction, multiplication and division: 4. When querying, give the query result the word

##5.

php query and multi-condition query

Introduction: This article shares with you the code and examples of using PHP to implement single-condition and multi-condition queries. It is very Practical, friends in need can refer to

##6.

mysql advanced (5) multi-condition query with OR in the data table

Introduction: The OR keyword can be combined with multiple conditions to query. When using the OR keyword:

7. PHP processing of HTML encoded strings

Introduction: When I wrote a PHP script to access the database today, I found that the Chinese strings were stored using HTML encoding (for example, the HTML encoding for the Chinese character "Mao" is " 毛"), so that when performing conditional query on this field, it is not possible to use Chinese for query, but it must be converted into encoding before conditional matching. When converting readable characters and HTML-encoded characters in PHP, you need to use the htmlentities and html_entity_decode functions. So I wrote the following query statement, ...

8. How to determine if the data is greater than N when querying the data? Is the query recursive?

Introduction: For example, the database has 300,000 pieces of data. Now according to the query, there are 30,000 pieces of data that match the conditions. Fetching too much at one time may be slow or other problems. I want to fetch 10,000 three times each time. After taking this as an example, how should it be implemented? Use recursion? Let me know. Thank you! ! ! Also, if you look up the numbers in two tables...

9. PHP’s processing of HTML encoded strings

Introduction: Today when I was writing a PHP script to access the database, I found that the Chinese strings were stored using HTML encoding (such as the Chinese character "Mao"). "The corresponding HTML encoding is "毛"), so that when performing conditional queries on this field, you cannot directly use Chinese to query, but you must convert it into encoding before performing conditional matching. When converting readable characters and HTML-encoded characters in PHP, you need to use the htmlentities and html_entity_decode functions. So write the following query statement, ...

10. sql multi-condition query

Introduction: To implement Multi-condition query, when the value is 0, it is unlimited. How to use sql to implement it. For example: querying a certain type of store in a certain area may be unlimited. The type is Chinese food. When querying, there is no need for where region = value, but only where type = Chinese food. , select the area as Beijing and the type as Chinese food query...

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