[Zhuantang learning notes] basic SQL query statements (single-Table query and multi-Table query)SQLQueryBasic1. Single Table query
It is also called projection.
Basic query statement Structure
Select column from table
* Not all ot
As a small programmer, in the day-to-day development can not be avoided with where in and like to deal with, in most cases we pass the parameters of simple quotes, sensitive words escape directly after the SQL, execute the query, fix. If one day you inevitably need to improve SQL query performance, need a one-time wher
' --true display, false --where birthday> ' 1990-01-01 ' SELECT sex from info WHERE SEX was not NULL SELECT SNAME from info WHERE SNAME like '% Month ' ------back up INFO table to Info--bak --1 Info_bak -- 2 Insert query Data Select *into Intfo_bak from INFO-two functions to create a new table Insert query data --note constraint does not back up identity property backup (Identity) SELECT * into Inf
This article mainly introduces thinkphp range query, statistical query, and SQL direct query. It analyzes the common Query Techniques of ThinkPHP in details in the form of examples, which is very useful, for more information, see
This article mainly introduces thinkphp range
SQL two simple paging query methods, SQL paging Query Method
In the past, we may have used the skip and take method of linq for paging queries, but few of them write SQL paging queries by themselves, because most of the time, we are calling others' methods.
I recently saw
This article mainly introduces thinkphp range query, statistical query, and SQL direct query. it analyzes the common query techniques of ThinkPHP in details in the form of examples, which is very useful, for more information about the thinkphp interval
What if SQL fuzzy query encounters a null value ?, SQL fuzzy query is blank
Author: iamlaosong
The SQL query statement uses % for fuzzy query. in the program, users are generally requir
After sqlserver2005, MSSQL began to use the recursive query method. Compare the methods for writing stored procedures or functions at the beginning. This method is simpler and more flexible.
Oracle also has its own tree structure recursive query method, connect
Next I will write a piece of SQL code by myself, and briefly comment out some usage of the CTE shar
Summary of the practical methods for optimizing SQL query statements, and the practical use of SQL query statements
Optimization of query statements is a way to optimize SQL efficiency. You can optimize
) Select DATEADD (Wk,datediff (Wk,0,getdate ()), 0) query yesterday Date: Select CONVERT (Char,dateadd (dd,-1,getdate)), 111 //111 is the style number, (100-114) query the first day of the month Date: Select DATEADD (mm, DATEDIFF (Mm,0,getdate ()), 0) as FirstDay query last day of the month Date: Select DATEADD (M S,-3,dateadd (mm, DATEDIFF (M,0,getdate ()) +1, 0
Yesterday's SQL Server query performance optimization-index creation principle (I) mainly introduced the principle. today are some of the main principles and checks the created indexes.
Iii. indexing principles
In general, building indexes depends on the data usage scenarios. In other words, which SQL statements are commonly used to access data? Are these stateme
This paper illustrates the thinkphp interval query, statistical query and SQL direct query. Share to everyone for your reference. The specific methods are as follows:
First, the interval query:
Copy Code code as follows:
$data [' ID ']=array (Array (' GT ', 4)
Tags: union function combination join like multiple blog multi-column subqueryUnit03:sql (Basic query), SQL (associative query) Column Aliases when the column queried in the SELECT clause is a function or an expression, the name of the field in the result set that is queried is the name of the function or expression.
Tags: style blog http color using AR SP data divShortly before the project was developed, the Entity Framework was used to process data. Because I am not too much research on EF, but will use only, but in one need to query the results need to correlate 3, 4 tables to query the results, and query efficiency is also required. But personally, there is a situation in
/*Author: A niu (NIU kunliang) QQ: 273352165 MSN: niukl@hotmail.comDisclaimer: free of charge. Please keep this informationIf you have any questions, please tell me!*/When we use stored procedures, we sometimes have to use dynamic queries to combine query conditions. For example, the following code:
Create
Proc
Usp_search
@ City
Int
As
Begin
Declare
@ SQL
Varchar
(
SQL pagination query method summary, SQL pagination Query Method
Requirement: query the table dbo. Message, with 10 entries per page and 2nd pages
1: TOP ()
SELECT TOP(20) * FROM dbo.Message WHERE Code NOT IN(SELECT TOP(10) Code FROM dbo.Message)
2: BETWEEN * AND *, Row_Numb
; where ($ data)-> count (); // The array operation is more standard.
You can use SQL to directly query and perform more operations flexibly.
A. The primary number of queries processes the data read. The result set is returned successfully. if the query fails, the return value is boolean false.
$ M = M ();
$ Result = $ m->
total_logical_reads/execution_count gt; 4000 order by total_elapsed_time/execution_count DESC;
There is an article on the red/Black Alliance: SQL Server parameterized query where in and like implementation
This article contains the following paragraph:
The author has a sentence: "But there is no substantial difference between this writing method and direct SQL
SQL Server connection query details, SQL Server Query details
When querying multiple tables, we often use "join query ". Connection is the main feature of the relational database model and a symbol that distinguishes it from other types of database management systems.
What i
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