xquery if statement

One, if statementIn PL/SQL, keywords such as if, then, else, elsif, endif are used to perform conditional logicSyntax format:if conditions 1 Then Statement 1elsif conditions 2 Then Statement 2Else Statement 3End If; Example 1: Practice If structureSolution: Note the program in:Second, Case statementSyntax structure: Case variables when value 1 Then

SQL GROUP BY statement, sqlgroupby statement A group by statement is often required for Aggregate functions (such as SUM.Group by statement The group by statement is used in combination with the aggregate function to GROUP result sets based on one or more columns.SQL GROUP B

In our program development, it may be necessary to repeat the use of a piece of code or a function, such as the need to enter "1*2*3*4...*100", if the human input, it will waste a lot of time, but also very cumbersome, but in this case, there is a good way, is to use our PHP loop control statements, the use of PHP loop control statements, you can quickly complete the calculation, in PHP, we provide four kinds of loop control statements: While, Do...while, for, and foreach. This chapter, first of

the types of statements include : Declaration statements, expression statements, select statements, loop statements, jump statements, exception statements1. Declare statement citation: Enter a new variable or constant. Variable declarations can optionally assign values to variables. A value must be assigned in a constant declaration.For example:int i = 0;//declares the variable i and assigns a value, or it can not be assigned.Double D;"//" means a lin

Statement:The types of statements include declaration statements, expression statements, select statements, loop statements, jump statements, exception statements.One: declaration statement: Into the new variable and solid. Variable declarations can optionally assign values to variables. The value must be assigned in the re-const declaration.Cases:int i = 0; Declare the variable i and assign a value, or you can not assign a value.Double A;Two: express

Understand the With statement and pythonwith statement in Python Some tasks may need to be configured in advance and cleaned up afterwards. In this scenario, the with statement of Python provides a very convenient processing method. A good example is File Processing. You need to obtain a file handle, read data from the file, and then close the file handle. Withou

Number of sub-classes · C language-condition statements and C language statements First of all, let's talk about the theoretical knowledge. There are three structures in programming: sequential structure, conditional structure, and cyclic structure. If they are expressed using flowcharts: In C, how can we use these three structures flexibly? This requiresControl statement. WhileCondition StatementIs one of the control statements. Generally, ther

Some differences between the INSERTINTOSELECT statement and the SELECTINTOFROM statement are described. For more information, see the following description and conditions. Some differences between the insert into select statement and the select into from statement are described. For more information, see the following

SQL statement optimization principle and SQL statement optimization. SQL statement optimization principle: optimize SQL statements to process more than one million data to improve query speed: 1. avoid using the where clause as much as possible! Or operator. Otherwise, the engine will discard the SQL statement optimiza

Common SQL statement optimization skills (1) and SQL statement optimization skillsTo improve the efficiency of SQL statement execution, the most common method is to create an index and avoid full table scan. We will organize some common SQL optimization techniques to avoid full table scanning. A simple optimization may increase your SQL Execution efficiency by se

SQL statement optimization introduction and SQL statement Optimization 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 the field in the where clause. When creating a table, NULL is the default value, but not null should be used in most cases, or a special value, such as 0, -1

With statement Executes a series of statements on an object. With objectstatementsEnd With Parameters Object The required part. Can be either an object name or a function that returns a value to an object. Statements The required part. One or more commands that will be executed on object . Description The WITH statement can be used to execute a series of statements on the specified object, but it does not

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_name2N

SQL statement join Table query and SQL statement join query Answers to questions about SQL statement join Table query 1. Create two databases: Database A (table a) and database B (table B ). 2. allocate the same account permissions to the two databases. 3. Use the following statement during query: The Code is as foll

A for loop is the most complex loop structure in PHP. Its behavior is similar to that in C. In PHP, the number of times the same code set is executed The meaning of for in php A for loop is the most complex loop structure in PHP. Its behavior is similar to that of C language. In PHP, the number of times the same code set is executed A for loop is just a little more code and is added to it in a loop. The common tasks involved in a loop are:Set the initial values of some counter variables.Check t

PHP fails to execute the SQL statement, but the current problem that the same statement can be executed in MYSQL is that some tables in the same database can be queried, and some tables cannot be queried. However, these statements can be normally executed in mysql ------ solution ------------------ check in one case, LZ can be combined into an SQL statement on th

"A project of Php+mysql" There is a user, username is admin, password is admin. The query statements are: $sql="select * from table_project where a_username='{$username}' and a_password='{$password}';"; Then query: $res=mysql_query($sql);……省略 Because of preventing SQL injection, I wanted to escape before the SQL statement query, so I escaped with Addslashes to the $sql statement, but it went wrong. $sql=ad

ExecuteGlobal statement Execute multiple statements specified in the global namespace of the script. ExecuteGlobal statement StatementA parameter is a string expression that contains one or more executable statements. InStatementParameters can contain multiple statements and are separated by colons.Description In VBScript,X = yThere are two ways to explain. The first method is to assign a valueYAssignedX.

Label:The person who writes the program often needs to analyze whether the SQL statement that has been written has been optimized, and how fast the server responds, this time it needs to use the statistics state value of SQL to view it. by setting Statistics we can view the system situation when executing SQL. The options are Profile,io, time. Introduced as follows: SET STATISTICS profile on: Displays the time, in milliseconds, that is required to par

Property Let statement In the Class block, declare names, parameters, and code, which form the body of the property procedure for the assignment (set). [Public | Private] Property Let name ( [arglist,] value)[statement][Exit Property] [statement]End Property Parameters Public Indicates that the property Let procedure can be accessed by all other procedures in