query optimization techniques in sql server

utilization is significantly lower than the first one. 3. Influence of query Table order The order of the list in the table following the from will have a performance impact on SQL, and with no indexes and no statistical analysis of the tables by Oracle, Oracle will be linked in the order in which the tables appear, so that the order of the tables is not the same as the data that is consuming the

Label:Original: SQL Server 2012:SQL Server architecture--The life cycle of a query (part 1th)To reduce the scope of the read operation, this article first looks at a simple select query and then introduces additional procedures re

1. SQL like method for time query processing the SQL data table has a savetime (smalldatetime type) field with two records in the table with Savetime value: 2005-3-8 12:12:00 and 2005-6-6 14:02:02 I can not find anything with the following statement SELECT * from soft where soft.savetimelike '%2005-3-8% ' SQL

condition cannot be indexed , such as: YS_DF>CX_DF, cannot be optimizedQC_BH | | Kh_bh= ' 5400250000 ', optimized processing: qc_bh= ' 5400 ' and kh_bh= ' 250000 'Iv. OtherOracle's hints feature is a relatively strong feature and is a complex application, and hints are only a recommendation to Oracle, and sometimes Oracle may not follow the prompts for cost considerations. According to practical application, the developer is generally not recommended to apply the Oracle hint, because the perfor

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

Using regular expressions in SQL Select Name,email from user where email Regexp "@163[.,]com$"; Using REGEXP in SQL statements has a greater impact on performance. Second, use the rand () function to obtain random data Rand (); random number function 1. Random sort mysql> Select * from Hello ordering by rand (); 2. Random column Extraction 3 mysql> select * FROM Hello ORDER by rand () limit 3; Third,

cursors are inefficient and should be considered for overwriting if the cursor is manipulating more than 10,000 rows of data.26. Before using a cursor-based method or temporal table method, you should first look for a set-based solution to solve the problem, and the set-based approach is generally more efficient.27. As with temporary tables, cursors are not unusable. Using Fast_forward cursors on small datasets is often preferable to other progressive processing methods, especially if you must

partial database backup and file backup. The new restore statement allows you to use full or partial database backup and record file backup for restoration. These replace the dump and load statements in earlier versions of SQL Server. For a complete list of new statements and options for SQL Server 7.0 and

number of rows to get the cost of that operator, which is the cost of all these operators.Because the cost comes from the bottom line value and is independent of your hardware speed, in each SQL Server appliance (Like-for-like version. Bo Main note: not related to the version. The cost of generating each plan is the same.Because our select query is very simple,

Optimization of SQL massive data query and non-use like processing solutions, data query like 1. To optimize the query, try to avoid full table scanning. First, consider creating an index on the columns involved in where and order. 2. Try to avoid null value determination on

Optimization of SQL massive data query and non-use like processing solutions, data query like 1. To optimize the query, try to avoid full table scanning. First, consider creating an index on the columns involved in where and order.2. Try to avoid null value determination on

,'YYYYMMDD') Rangebetween thePreceding Currentrow)End asf70115_70011, Case whenA.c_date>To_char (sysdate-3,'YYYYMMDD') Then sum(VALUEF1) Over(Partition byA.code,a. Year Order byTo_date (A.c_date,'YYYYMMDD') Rangebetween thePreceding Currentrow)End asf70104_70011, Case whenA.c_date>To_char (sysdate-3,'YYYYMMDD') Then sum(VALUEF6) Over(Partition byA.code,a. Year Order byTo_date (A.c_date,'YYYYMMDD') Rangebetween thePreceding Currentrow)End asf70126_70011, Case whenA.c