truncate statement in sql

scan, such as:Select ID from t where num=10 or num=20You can query this:Select ID from t where num=10UNION ALLSelect ID from t where num=20 5.in and not in should also be used with caution, otherwise it will result in full table scans, such as:Select ID from t where num inFor consecutive values, you can use between instead of in:Select ID from t where num between 1 and 3 6. The following query will also cause a full table scan:Select ID from t where name like '%abc% 'To be more efficient, consi

scan, such as:Select ID from t where num=10 or num=20You can query this:Select ID from t where num=10UNION ALLSelect ID from t where num=20 5.in and not in should also be used with caution, otherwise it will result in full table scans, such as:Select ID from t where num inFor consecutive values, you can use between instead of in:Select ID from t where num between 1 and 3 6. The following query will also cause a full table scan:Select ID from t where name like '%abc% 'To be more efficient, consi

Tags: style blog http io ar color OS using SPSource: The difference between @ @IDENTITY and @ @ROWCOUNT in SQL Drip 31-sql statementdifference between @ @IDENTITY and @ @ROWCOUNT in SQL statementsAfter an INSERT, SELECT into, or bulk copy statement is complete, the @ @IDENTITY contains the last identity value generated

SQL statement-case when then else end, SQL-case Output the following results based on the preceding table information: The following are the database and table structure data: create table DeptSales(deptID int,SubjMonth int ,sales int ,deptname varchar(50)) insert into deptsales (deptid ,subjmonth,sales) values (1,1,55);insert into deptsales (deptid ,subjmon

Recently, my colleagues in the Company Met a requirement to implement a function and want to use an sq statement. He asked me to see how to implement SQL. Since we talked about minimizing interaction with databases during the early stage of training, we don't need to use two SQL statements if we can extract one SQL

Copy Code code as follows: --begin Index (index) analysis optimization related SQL --Returns an index with more than 25% of the current database fragmentation rate --Running this statement scans a lot of data pages --Avoid running when the system load is relatively high --Avoid running when the system load is relatively high DECLARE @dbid int Select @dbid = db_id () SELECT O.name as tablename,s

Tags: databaseSQL databases T-SQL statement queryData files for attached databases650) this.width=650; "src=" https://s3.51cto.com/wyfs02/M01/96/06/wKiom1kcDfOB6lJHAAtJeP4PO9c190.jpg "style=" float : none; "title=" 1.jpg "alt=" Wkiom1kcdfob6ljhaatjep4po9c190.jpg "/>The category in the query table is the fruit of the factory date after 201-04-01650) this.width=650; "src=" Https://s3.51cto.com/wyfs02/M02/96/0

Domain -- create a Data Value DomainAlter Domain -- change domain definitionDrop Domain -- delete a domain from the database-- Data ControlGrant -- Grant the user access permissionDeny-Deny User AccessRevoke -- revoke User Access Permissions-- Transaction controlCommit -- end the current transactionRollback -- abort the current transactionSET transaction -- define the data access features of the current transaction-- Programmatic SQLDeclare -- set the cursor for the queryExplain -- describe the

The earliest notation: withT as(SELECT Case whenCol1 is NULL ORCol1=N"' ThenCol2ElseCol1End asCode, Case whenCol1 is NULL ORCol1=N"' Then 1 Else 0 End asFlag fromYMWHEREcol_076between '2018-07-25' and '2018-08-03' andcol_478=N'xx' andcol_346 likeN'%dd%'), D as(SELECTCode,province,city fromAdds)SELECTProvince asProvince, City asCityCOUNT(1) Number of votes from (SELECTa.dr_250 asprovince,a.dr_251 asCity fromTINNER JOINTB asA ona.dr_203=T.codeWHERET.flag=0 UNION All SELECTD.province,d.c

SQL statement + select top usage of "Fetch 10th to 20th records from a data table", 10th SQL statements 1. First, select top usage: For more information, see the differences between select top n * from and select * from. Select * from table -- retrieve all data and return unordered Sets Select top n * from table -- obtains the first n records based on the data st

Displays information about all tables or views in a database of an SQL Server. The difference between SQL Server 2000 and 2005 lies in the red part. The following statement is used to obtain information about all tables. Replace "U" with "v" with "U" to obtain information about all views. SQL Server 2000 Select sy

SQL statement concise tutorial for linux --- TRIM, SQL concise tutorial --- trim The TRIM function in SQL is used to remove the character header or end of a string. The most common purpose is to remove the leading or trailing blank spaces. This function has different names in different databases: MySQL: TRIM (), RTRI

Label:Many people don't know how SQL statements are executed in SQL Server, and they worry that the SQL statements they write will be misunderstood by SQL Server. Like what: Name=> 10000 and execution: Name=' Zhangsan ' Some people do not know whether the executio

, execution time: 156.3 seconds) SELECT … FROM EMP E WHERE SAL> 50000 AND JOB = ‘MANAGER’AND 25 (Efficient, execution time: 10.6 seconds) SELECT … FROM EMP E WHERE 25 4. Avoid '*' in the select clause '*'. When listing all columns in the select clause, it is convenient to reference '*' using dynamic SQL columns. unfortunately, this is a very inefficient method. in fact, Oracle converts '*' into all column names in sequence during parsing. This is

SQL Study Notes (14) ------------ data table, SQL statement for creating a data table Operations on Data TablesBasic Database OperationsWith MySQL, you can choose between the three basic database table formats (version 3.23. When creating a table, you can tell MySQL which table type it should use for the table. MySQL will always create a. frm file to save the tab

Tags: trunc apache business upd explain fixed different log changesYesterday Qi, share with you the optimization of the index in SQL optimization, today to talk to you, in the development process of high-quality code will also bring optimization There are a lot of tutorials on SQL optimization online, but it's messy. Qi organized a bit, write to share with you, where there are errors and deficiencies, but a

convert ' * ' to all column names in the process of parsing, which is done by querying the data dictionary, which means more time is spent(4) Reduce access to the database: Oracle has done a lot of work internally: Parsing SQL statements, estimating index utilization, binding variables, reading data blocks, etc.;(5) Reset the ArraySize parameter in Sql*plus, sql

. d Where ..... 12. Note: Five minutes ahead of schedule reminderSQL: Select * from Schedule where datediff ('minute ', F Start Time, getdate ()> 5 13. Note: One SQL statement is used to handle database paging.Select top 10 B. * From (select top 20 primary key field, sorting field from table name order by sorting field DESC) A, table name B where B. primary key field =. primary key field order by. sorting F

EXISTS (SELECT 1From T_orders bWHERE b.customer_id = 12and a.employee_id = b.sales_rep_id);--T_EMPLOYEES.DEPARTMENT_ID has indexSELECT a.*From T_employees AWHERE a.department_id = 10and EXISTS(SELECT 1 from t_orders b WHERE a.employee_id = b.sales_rep_id);SELECT a.*From T_employees AWHERE a.department_id = 10and a.employee_id in (SELECT b.sales_rep_id from t_orders b);--FBIDROP TABLE T_FBI;CREATE TABLE T_FBI asSELECT ROWNUM RN, Dbms_random. STRING (' Z ', ten) NAME, Sysdate + dbms_random. VALUE

practical use, only in two tables connected with the restrictions, it will have practical significance, the following see the inner connectionInternal connectionIf it is understood in steps, the inner connection can be considered as a cross-linking of two tables, and then by adding a restriction (in SQL through the keyword on) to exclude a subset of the rows that do not meet the criteria, the result is an inner connection. The above figure, if I add