sql query with nolock

optimistic row version control lock No prompt not locked update NOLOCK not locked HOLDLOCK sharing update UPDLOCK error Update TABLOCKX Error unlocked unlocked update other unlocked update * The specified NOLOCK prompt will make the table specified with this prompt read-only in the cursor. 16. Use Profiler to track the query, obtain the time required for the

results of multiple SELECT statements together, in which case it is necessary to combine the results of several SELECT statements, for example, to query all the employee information of company A and Company B, and then merge the results of the two queries together. The Union and UNION ALL keywords are used for the merge operation. Format: SELECT statement 1 UNION | UNION All SELECT statement 2 UNION | UNION All ............ Example:

Use pt-query-digest to find the SQL statement that is not suitable, pt-query-digestsql Overview of pt-query-digest1. Indexes can be executed more quickly, but there must be unreasonable indexes. If you want to find those indexes that are not very suitable and optimize them before they become problems, you can use the p

silent unlocked unlocked unlocked not locked NOLOCK unlocked unlocked unlocked HOLDLOCK shared share share update UPDLOCK error update update TABLOCKX error Unlocked not Lock update other unlocked unlocked Unlocked update * Specifies that the NOLOCK hint will make the table specified with this hint read-only in cursor. 16. Use Profiler to track the query, get th

First, simple query SQL (structured query Language) Structured Query language is a database query and programming language for accessing data and querying, updating, and managing relational database systems. ANSI (American National Standards Institute) claims that

SQLServer how to use the T-SQL command to query a database in which tables, convenient table operations, need friends can refer to the next SQLServer how to use the T-SQL command to query a database in which tables, convenient table operations, need friends can refer to the next 1.

1. query all tables in SQL: Select TABLE_NAME FROM database name. INFORMATION_SCHEMA.TABLES Where TABLE_TYPE = 'base table' after execution, you can see the names of all tables created by yourself in the database. 2. query all tables and columns in SQL: Select dbo. sysobjects. name as Table_name, dbo. syscolumns.

Next: T-SQL Dynamic Query (1)--IntroductionObjective:In the development of features, we often encounter scenarios such as the following: The application has a query function that allows the user to select the desired condition in many query conditions. This is also the focus of this series.But sometimes you may find th

SQL query statement "3": Multi-Table query (also called connection query, which is a connection query based on two tables)If a query needs to operate on multiple tables, it is called a connection

1. Query all tables in sql: Select table_name from database name. Information_schema. Tables Where table_type= ' BASE table ' is executed, you can see the names of all the tables in the database that belong to you 2. Query all tables and columns in sql:Select Dbo.sysobjects.name as TABLE_NAME, dbo.syscolumns.name as column_name from Dbo.syscolumns INNER JOIN

SELECT statement of the cursor. Lock prompt read-only optimistic value optimistic row version control lock No prompt not locked update NOLOCK not locked HOLDLOCK sharing update UPDLOCK error Update TABLOCKX Error unlocked unlocked update other unlocked update * The specified NOLOCK prompt will make the table specified with this prompt read-only in the cursor. 16. Use Profiler to track the

Advanced query technology is mainly related to multiple tables linked query technology, embedded SELECT statement subquery technology, the combination of multiple queries combined technology. 1. Connection Query You need to retrieve data from two or more tables at the same time. A link allows you to retrieve data from two tables or more than two tables at the s

Connection Query You can use the join operator to query multiple tables. Connection is the main feature of the relational database model and a symbol that distinguishes it from other types of database management systems. In the relational database management system, the relationship between data does not have to be determined when a table is created, and all information about an object is often stored in a

not close any opened cursor, and the scroll lock is retained until it is committed to maintain isolation of the extracted data. The type of the obtained scroll lock depends on the cursor concurrency option and the lock prompt in the SELECT statement of the cursor. Lock prompt read-only optimistic value optimistic row version control lock No prompt not locked update nolock not locked holdlock sharing update updlock error Update tablockx Error unlocked

1. query all tables in SQL:Select TABLE_NAME FROM database name. INFORMATION_SCHEMA.TABLES Where TABLE_TYPE = 'base table' after execution, you can see the names of all tables created by yourself in the database.2. query all tables and columns in SQL:Select dbo. sysobjects. name as Table_name, dbo. syscolumns. name AS Column_name FROM dbo. syscolumns inner join dbo. sysobjects ON dbo. syscolumns. id = dbo.

Label:Next: T-SQL Dynamic Query (3)--Static SQLObjective: There's a lot of talk about dynamic queries, and this article describes some of the ways to use dynamic SQL to solve dynamic queries.Why use Dynamic sql: in many projects, dynamic SQL is widely used and even misused,

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

Label:IntroductionSee a popular blog today. NET Senior Engineer face questions of SQL, asked to find the highest score of each department, and by the department number, the student number in ascending order. This query is more complex, but also more typical, since the use of ORM, a long time did not write SQL statements, so I studied the next, I also wrote a: w

' Teacher ' (' Tid ' int (one) not NULL auto_increment,' Name ' varchar (DEFAULT NULL),' job_title ' varchar DEFAULT NULL,' Major ' varchar DEFAULT NULL,PRIMARY KEY (' tid ')) Engine=innodb auto_increment=6 DEFAULT Charset=utf8; Tutor Table Data Insert INTO ' teacher ' (' tid ', ' name ', ' Job_title ', ' major ') values (1, ' Shen ', ' Professor ', ' image '), (2, ' Liu ', ' Professor ', ' database '), (3, ' Yellow ', ' associate Professor ', ' machine learning '), (4, ' Jarvis

Tags: SQL statement electronic win style SPAN different statement column DTS --Connect remote SQL or insert data with OPENROWSET --if only temporary access, you can directly use OPENROWSET --Query Example Select * from OpenRowset('SQLOLEDB' ,'SQL Server name';'User name';'Password', database name. dbo. Table name)