sqlserver 支持定位当前页,自定义排序的分页SQL(拒绝动态SQL)
1,场景:根据学生编号查询,返回该学生所在班级的所有学生。支持分页、自定义排序及结果集自动定位到查询条件的学生编号所在页。代码如下:
CREATE PROC [dbo].[Sp_testpagerandsorting] (@GroupID INT,
@CurrentId INT,
@TimeFrom DATETIME,
@TimeTo DATETIME,
@OrderBy CHAR(50),
@PageSize INT,
@CurrentPage INT)
AS
SET nocount ON
BEGIN
DECLARE @StartNumber INT,
@EndNumber INT,
@CurrentIdRowNumber INT,
@RecordCount INT,
@EndPageIndex INT
DECLARE @RowNumberTable TABLE (
rownumber INT IDENTITY (1, 1),
id INT )
--step 1: Build sort id list -------------------------------------------------------
INSERT INTO @RowNumberTable
(id)
SELECT sm.id AS id
FROM dbo.test sm WITH (nolock)
WHERE indate BETWEEN Coalesce(@TimeFrom, indate) AND
Coalesce(@TimeTo, indate)
AND sm.groupid = @GroupID
ORDER BY CASE
WHEN @OrderBy = 'InDate desc' THEN ( Row_number() OVER (ORDER BY indate DESC))
WHEN @OrderBy = 'InDate asc' THEN (Row_number() OVER (ORDER BY indate ASC))
WHEN @OrderBy = 'Id asc' THEN (Row_number() OVER (ORDER BY sm.id ASC))
WHEN @OrderBy = 'Id desc' THEN (Row_number() OVER (ORDER BY sm.id DESC))
WHEN @OrderBy = 'Name asc' THEN (Row_number() OVER (ORDER BY sm.name ASC))
WHEN @OrderBy = 'Name desc' THEN (Row_number() OVER (ORDER BY sm.name DESC) )
END
--step 2: Reset page index with current id -----------------------------------------
IF @CurrentIdNumber > 0
BEGIN
SELECT TOP 1 @CurrentIdRowNumber = rownumber
FROM @RowNumberTable
WHERE id = @CurrentIdNumber
IF @CurrentIdRowNumber > 0
BEGIN
IF @CurrentPage = 0
BEGIN
SET @CurrentPage = Ceiling(CAST(@CurrentIdRowNumber AS DECIMAL) / CAST (@PageSize AS DECIMAL))
END
END
END
ELSE
BEGIN
IF @CurrentPage = 0
BEGIN
SET @CurrentPage = 1
END
END
--step 3: Set recordCount -----------------------------------------
SELECT @RecordCount = COUNT(1)
FROM @RowNumberTable
--step 4: Calc startNumber & endNumber -----------------------------------------
SELECT @StartNumber = @PageSize * ( @CurrentPage - 1 ),
@EndNumber = @PageSize * ( @CurrentPage - 1 ) + @pageSize,
@EndPageIndex = Ceiling(CAST(@RecordCount AS DECIMAL) / CAST(@PageSize AS DECIMAL))
IF @CurrentPage = @EndPageIndex
BEGIN
SET @EndNumber = @RecordCount
END
--step 5: Get sorted id of current page -----------------------------------------
;WITH a
AS (SELECT TOP (@EndNumber - @StartNumber) id,
rownumber
FROM (SELECT TOP (@EndNumber) id,
rownumber
FROM @RowNumberTable) AS b
ORDER BY rownumber DESC)
--step 6: Return current page idList -------------------------------------------------------
SELECT [ID],
[GroupID] [Name],
[Address]
FROM dbo.test sm WITH(nolock)
INNER JOIN a
ON a.id = sm.id
ORDER BY a.rownumber
-- step 7:return current page & record count ----------------------------------
SELECT @CurrentPage AS currentpage,
@RecordCount AS recordcount
END
2,简单条件的,动态where语句(关于Like查询的动态where,建议使用笨办法做)
代码如下:
CREATE PROC [dbo].[Getstudentlistbycondition] @Name NVARCHAR(20),
@Class INT
AS
SET nocount ON
BEGIN
BEGIN
SELECT [Name],
[class]
FROM [testtable]
WHERE [Class] = CASE
WHEN @Class > 0 THEN @Class ELSE [Class] END
AND [name] = CASE
WHEN @Name '' THEN @Name ELSE [Name] END
END
END

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB

MySQL/InnoDB supports four transaction isolation levels: ReadUncommitted, ReadCommitted, RepeatableRead and Serializable. 1.ReadUncommitted allows reading of uncommitted data, which may cause dirty reading. 2. ReadCommitted avoids dirty reading, but non-repeatable reading may occur. 3.RepeatableRead is the default level, avoiding dirty reading and non-repeatable reading, but phantom reading may occur. 4. Serializable avoids all concurrency problems but reduces concurrency. Choosing the appropriate isolation level requires balancing data consistency and performance requirements.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.

MySQL index cardinality has a significant impact on query performance: 1. High cardinality index can more effectively narrow the data range and improve query efficiency; 2. Low cardinality index may lead to full table scanning and reduce query performance; 3. In joint index, high cardinality sequences should be placed in front to optimize query.

The MySQL learning path includes basic knowledge, core concepts, usage examples, and optimization techniques. 1) Understand basic concepts such as tables, rows, columns, and SQL queries. 2) Learn the definition, working principles and advantages of MySQL. 3) Master basic CRUD operations and advanced usage, such as indexes and stored procedures. 4) Familiar with common error debugging and performance optimization suggestions, such as rational use of indexes and optimization queries. Through these steps, you will have a full grasp of the use and optimization of MySQL.

MySQL's real-world applications include basic database design and complex query optimization. 1) Basic usage: used to store and manage user data, such as inserting, querying, updating and deleting user information. 2) Advanced usage: Handle complex business logic, such as order and inventory management of e-commerce platforms. 3) Performance optimization: Improve performance by rationally using indexes, partition tables and query caches.


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