[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
' --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
Mandatory SQL statement (6) Data Query and SQL statement Data Query
1. Basic Query1) rename a columnSelect name as 'name' from Table name2) define constant ColumnsSelect = 'is 'From table name3) top usage: percent-- In this way, you can obtain the first 20% fields.Select top 20 percent * from Table Name4) Remove duplic
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
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
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
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:
$data [' ID ']=array (Array (' GT ', 4)
Tags: union function combination join like multiple blog multi-column subqueryUnit03:sql (Basic query), SQL (associative query) Column Aliases when the column queried in the SELECT clause is a function or an expression, the name of the field in the result set that is queried is the name of the function or expression.
Tags: style blog http color using AR SP data divShortly before the project was developed, the Entity Framework was used to process data. Because I am not too much research on EF, but will use only, but in one need to query the results need to correlate 3, 4 tables to query the results, and query efficiency is also required. But personally, there is a situation in
My Date
The first date format we get is this: 2009-2-12 or 2009-3-3 or 2009-10-12, we can do this by combining SQL statements: (three examples)
The code is as follows
Copy Code
@1select * from user where birthday> ' 2009-2-3 ' and birthday
This allows us to find all user information that includes 2009-2-3 and is greater than 2009-2-3.
@2 If that's how we mix it.
The code is as follows
Copy Code
SQL pagination query method summary, SQL pagination Query Method
Requirement: query the table dbo. Message, with 10 entries per page and 2nd pages
1: TOP ()
SELECT TOP(20) * FROM dbo.Message WHERE Code NOT IN(SELECT TOP(10) Code FROM dbo.Message)
2: BETWEEN * AND *, Row_Numb
; where ($ 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->
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
Summary of simple SELECT query statements in SQL, and SQL SELECT query statements
-- Scott users cannot use it. Use system to log on-- Modify scott account to unlockAlter user scott account unlock;-- Reset the password identified to be recognizedAlter user scott identified by tiger;
-- Select the scott user department
SQL like usage fuzzy query and SQL fuzzy query
Fuzzy query:
References: http://www.w3school.com.cn/ SQL/SQL _wildcards.asp
When searching for data in a database, you can use the
SQL query a specified date and time record SQL statement and query an instance
Create a table with the following abc structure:Create table 'cc'. 'loup '('Id' INT (4) not null AUTO_INCREMENT,'Datetimes 'INT (4) NULL,'Ipaddress' VARCHAR (20) NULL,Primary key ('id ')) ENGINE = MYISAMInsert data in batchesInsert into 'lou
SQL query specify date time record SQL statement and query instance
First create a table ABC structure is as followsCREATE TABLE ' cc '. ' Loup ' (' ID ' INT (4) Not NULL auto_increment,' DateTimes ' INT (4) NULL,' IPAddress ' VARCHAR NULL,PRIMARY KEY (' id ')) ENGINE = MYISAMThen BULK INSERT dataINSERT into ' loup '
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