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SQL connections (2) -- SQL Reading Notes, SQL Reading Notes Chapter 1 in SQL Learning Guide 1.4 outer connections In multi-table join, the connection condition may not match all rows in the table. For example, when the account table is connected to the customer table, the value of the cust_id column in the account tabl

SQL UNION operatorThe UNION operator is used to combine the result set of two or more SELECT statements.Note that the SELECT statement inside the UNION must have the same number of columns. The column must also have a similar data type. Also, the order of the columns in each SELECT statement must be the same.SQL UNION SyntaxSELECT column_name (s) from Table_name1unionselect column_name (s) from table_name2Note: By default, the UNION operator chooses a

Static SQL, dynamic SQL, and static SQL Static 1. Common MemberCommon members belong to objects.Call with object 2. Static membersStatic members belong to the classCalled by Class Name Class FenBi{Public int length; // common memberPublic string color ;//} Static keywords Static methods cannot contain common members. The common method can contain static members.

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

database parameterized ModeThere are two ways to parameterize a database, simple and mandatory (forced), and the default parameterization is "simple" by default.In simple mode, if the SQL is sent every time, unless it is exactly the same, it will be recompiled (special circumstances will be automatically parameterized, it is the focus of this article)The mandatory mode is to force the Adhoc SQL to be parame

After a DML statement is executed, the results of the DML statement are stored in four cursor attributes, which are used to controlProgramProcess or understand the program status. When running a DML statement, PL/SQL opens a built-in cursor and processes the result. The cursor is an area in the memory that maintains the query result. The cursor is opened when running the DML statement and closed after completion. Only

In fact, this is also a problem at work. To tell the truth, I am not willing to do it myself. I also want to write statements for queries, but I have not thoroughly studied this kind of information,Write SQL statements in JavaProgramAt the same time, I chose to be lazy. First, if it is golden, of course there is no need to say that the Direct Write statement is similar to select. If it is PL/SQL, it is not

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 dbo.sysobject s on dbo.syscolumns.id = Dbo.sysobjects.id Where (dbo.sysobjects.xtype = '

' 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

About T-SQL and SQL Enterprise Manager, SQL Enterprise After reading the database video, we often use two methods in the video. One is the SQL Enterprise Manager, and the other is the T-SQL (Tansact-SQL ). For the first method, it

server | sqlserver | data | data type | conversion Why not let SQL Server automatically convert the data type in SQL command for you Report Date: 12/5/2003 Prepared by: Zheng Ye Article last modified on 2004-2-16 The information in this article applies to: ü Microsoft SQL Server 2000, 7.0 Problem statement: One day, execute SELECT * FROM XXX_ORIGINAL_20031205

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. sysobjects. id Where (dbo. sysobjects. xtype = 'U') AND (NOT (dbo. sysobjects. name LIKE '

Topic: Consumers from Madrid with fewer than 3 orders Build table: Copy Code code as follows: SET NOCOUNT ON--When SET NOCOUNT is on, the count is not returned (representing the number of rows affected by Transact-SQL statements). Returns the count when SET NOCOUNT is off Use SY Go If OBJECT_ID (' dbo. Orders ') is not null DROP TABLE dbo. Orders Go If OBJECT_ID (' dbo. Customers ') is not null DROP TABLE dbo. Customers Go CREATE

1. View the version of the databaseSELECT @ @versionSeveral common types of SQL Server patched version numbers:8.00.194 Microsoft SQL Server 20008.00.384 Microsoft SQL Server SP18.00.532 Microsoft SQL Server SP28.00.760 Microsoft SQL Server SP38.00.818 Microsoft

1. view the database versionSelect @ version Common SQL server patch versions: 8.00.194 Microsoft SQL Server 20008.00.384 Microsoft SQL Server 2000 sp18.00.532 Microsoft SQL Server 2000 sp28.00.760 Microsoft SQL Server 2000 sp38.00.818 Microsoft

A big and comprehensive choice between SQL and functions: Who is a more effective SQL ?, More effective SQL Reprinted please indicate the source: jiq •'s technical Blog Note that the Oracle11g database is discussed here. It is not applicable to SQL Server, MYSQL, and other databases. 1. Problem Description There are t

Label:The optimization of SQL statements is to convert poorly performing SQL statements into the same performance SQL statements with the same purpose.AI automatic SQL optimization uses AI technology to automatically rewrite SQL statements to find the best-performing equival

1. sort by strokes of the Last Name: Select * From tablename order by customername collate chinese_prc_stroke_ci_as 2. database encryption:Select encrypt ('original password ')Select pwdencrypt ('original password ')Select pwdcompare ('original password', 'encrypted password') = 1 -- same; otherwise, different encrypt ('original password ')Select pwdencrypt ('original password ')Select pwdcompare ('original password', 'encrypted password') = 1 -- same; otherwise, different 3. Retrieve the fie

Many people do not know how SQL statements are executed in SQL Server, fearing that their written SQL statements will be misunderstood by SQL Server. Like what: SELECT * FROM table1 where name= ' Zhangsan ' and TID > 10000 and implementation: SELECT * FROM table1 where TID > 10000 and name= ' Zhangsan ' Some people

Tags: Audit SQL ServerIntroductionAudit is a feature after SQL Server 2008 that tells you "who did what when?" Specifically, auditing an instance of the SQL Server database engine or a separate database involves tracking and documenting events that occur in the database engine. Its bottom-level is based on extended events (Extented event), so its performance and