dynamic query in sql server

Label:Recently encountered a more interesting problem in the project, the online search for some methods, summarized here to share. We often encounter such a scenario: the need to query data, there are some query conditions, but when the query, we hope that when a condition is empty, then do not filter this condition, the main idea is to deal with the following:

First, let's take a look at a typical query form. This scenario is very simple: the customer name, order date, and owner are used as the filter conditions, and then find the order that meets the requirements. In those distant times, you may not need to write such a simple interface: Public interface iorderservice{Ilist Customer, datetime datefrom,Datetime dateto, int employeeid );} How to implement it, storage process, and ORM framework. It is assu

Grade> = 90 -- Use "logical expression" as the query condition ...... /* Logical expressions in SQL: Not: non And: corresponds Or: or */ Select * from Student -- Query the student table for a 19-year-old male student. Select * from Student where Sage = 19 and Ssex = 'male' -- Query the student whose age is 19 or 20 in

optimization of SQL dynamic Query stitching stringThe most primitive direct write: String sql= "select * from Testtables where 1=1";... Such code is inefficient, which affects the index reference of the databaseAs shown below:private void Testonemethod (){String querysql = "SELECT * from Testtables where 1=1";if (hason

stored procedure to execute Transact-SQL statements multiple times. Because the Transact-SQL statement itself remains unchanged, only the parameter values change, so SQL Server The query optimizer may reuse the execution plan that was generated on first execution. In gener

When writing stored procedures, you often encounter the need to splice SQL statements, generally only to perform the post-stitching statements using EXEC (@sql).Today, a stored procedure needs to get the results of a dynamic SQL query.Requirement Description: The cost value is queried in a table based on the ID value (

Label:In SQL Server, each query will find the shortest path to achieve its own goal. If the database accepts only one connection at a time, only one query is executed. Then the query is, of course, M.F.B. s to complete the work. For most databases, however, multiple queries

statement. The SQL Server Query Optimizer maySp_executesqlThe Transact-SQL statement of matches the execution plan of the previously executed statement to save the overhead of compiling the new execution plan. When using an execute statement, you must convert all parameter values to characters or Unicode and make th

Tags: Scroll method prepare win section data body multiple ICAThe most obvious feature of SQL differs from other programming languages is the order in which the code is processed. In a large number programming language, code is processed in encoded order, but in the SQL language, the first processed clause is the FROM clause, although the SELECT statement first appears, but is almost always finally processe

T-SQL query advanced-understanding the lock introduction in SQL Server, each query will find the shortest path to achieve their goals. If the database only accepts one connection, only one query is executed at a time. Therefore, q

the CTESELECT *FROM cte_name递归执行的语义如下： 将 CTE 表达式拆分为定位点成员和递归成员。 Run an anchor member to create the first call or datum result set (T0). Run the recursive member, use Ti as the input, and ti+1 as the output. Repeat step 3 until the empty set is returned. Returns the result set. This is the result of the T0 to Tn execution of UNION all. Anchor member is definedThe location of the query is the data setT0, and thenRecursive m

optimizing the execution plan for the database engine (this is not certain, it needs to be based on the implementation of the specific CTE), optimizing the execution plan, and naturally increasing the performance To better illustrate the ability of the CTE, here are two examples (transferred from the SQLite website document)Mandelbrot collection (Mandelbrot set)--The following code uses the SQLite 3.18.0 test through with the RECURSIVE Xaxis (x) as (VALUES ( -2.0) UNION all SELECT x+0.05

into' Student 'VALUES('8','Lee 48','123','male',' +','Jingan, Shanghai city'); INSERT into' Student 'VALUES('9','Zhang 39','111','male',' +','Shiyan, Hubei province'); INSERT into' Student 'VALUES('Ten','Lee 40','123','male',' +','Jingan, Shanghai city'); I. Querying 5~10 data MySQL Paging query: SELECT * FROM student limit 5, 10; Oracle Paging query: SELECT * FROM (select *,rownum rn from student) wh

it is to increase I/O.2. Vertical and horizontal partition table, reduce the size of the table (Sp_spaceuse)3. Upgrading hardware4, according to the query criteria, index, optimize the index, optimize access mode, limit the data volume of the result set. Note that the fill factor is appropriate (preferably using the default value of 0). The index should be as small as possible, using a Lie Jian index with a small number of bytes (refer to the creatio