Instance operations teach you how to use SQL Server Stored Procedures (1)

First, we will introduce what a stored procedure is: a stored procedure stores common or complex tasks with a specified name by writing SQL statements in advance, in addition, when such statements are stored in the database and different SQL statements can be executed according to the conditions, the database will be called to provide services with the same functions as the predefined stored procedure, you only need to call execute to automatically complete the command.

Let's take a look at the Stored Procedure syntax.

Create proc [edure] procedure_name [; number]
[{@ Parameter data_type}
[Varying] [= default] [Output]
] [,... N]

[
{Recompile | encryption | recompile, encryption}]

[For replication]

As SQL _statement [... n]

Parameters:

Procedure_name

Name of the new stored procedure. The process name must comply with the identifier rules and must be unique to the database and its owner.

To create a local temporary process, you can add a identifier (# procedure_name) before procedure_name. To create a global temporary process, you can add two identifier (# procedure_name) before procedure_name ). The complete name (including # Or #) cannot exceed 128 characters. The name of the specified process owner is optional.

　　What are the advantages of stored procedures?

1. the stored procedure can be compiled only when it is created. You do not need to re-compile the stored procedure every time you execute it. However, the SQL statement we usually use is compiled every time you execute it, therefore, using stored procedures can speed up database execution.

2. complex business logic and database operations are often encountered. In this case, SP is used to encapsulate database operations. When performing complex operations on the database (for example, performing update, insert, query, and delete operations on multiple tables ), this complex operation can be encapsulated in a stored procedure and used together with the transaction processing provided by the database. It can greatly improve database usage efficiency and reduce program execution time, which is very important in database operations with large data volumes. In terms of code, the separation of SQL statements and program code statements can improve the readability of program code.

3. You can set parameters for stored procedures. You can reuse the same stored procedure based on different input parameters to improve the code optimization rate and readability.

4. High security. You can set the type of stored procedure that only a user can use for a specified stored procedure:

(1) system stored procedure: starts with SP _. It is used to set the system and obtain information. related management work. For example, sp_help is used to obtain information about the specified object.

(2) The extended stored procedure starts with XP _ and is used to call the functions provided by the operating system.
Exec master .. xp_mongoshell 'Ping 10.8.16.1'

(3) User-Defined stored procedure, which is a common format of Stored Procedure

Template: Create procedure procedue_name [@ parameter data_type] [Output]
[With] {recompile | encryption} As SQL _statement

Explanation: Output: this parameter can be returned.

With {recompile | encryption} recompile: indicates that the stored procedure is re-compiled every time it is executed. encryption: the content of the created stored procedure is encrypted.

; Number

Is an optional integer used to group processes with the same name, so that the same group of processes can be removed with a drop procedure statement. For example, the process used by an application named orders can be named orderproc; 1, orderproc; 2, and so on. The drop procedure orderproc statement removes the entire group. If the name contains a bound identifier, the number should not be included in the identifier and the appropriate delimiters should be used before and after procedure_name.

@ Parameter

Parameters in the process. One or more parameters can be declared in the create procedure statement. You must provide the value of each declared parameter during execution (unless the default value of this parameter is defined ). A stored procedure can have a maximum of 2100 parameters.

Use the @ symbol as the first character to specify the parameter name. The parameter name must comply with the identifier rules. Each process parameter is only used for this process. The same parameter name can be used in other processes. By default, parameters can only replace constants, but cannot replace the names of table names, column names, or other database objects.

Data_type

The data type of the parameter. All data types (including text, ntext, and image) can be used as parameters for stored procedures. However, the cursor data type can only be used for output parameters. If the specified data type is cursor, the varying and output keywords must also be specified.

Note: There is no limit on the maximum number of output parameters that can be cursor data types.

Varying

Specify the result set supported by the output parameter (dynamically constructed by the stored procedure, and the content can be changed ). Only applicable to cursor parameters.

Default

The default value of the parameter. If the default value is defined, the process can be executed without specifying the value of this parameter. The default value must be a constant or null. If the like keyword is used for this parameter, the default value can contain wildcards (%, _, [], and [^]).

Output

Indicates that the parameter is a return parameter. The value of this option can be returned to Exec [ute]. The output parameter can be used to return information to the call process. The text, ntext, and image parameters can be used as output parameters. The output parameter using the output keyword can be a placeholder cursor.

N

It indicates that up to 2100 parameter placeholders can be specified.

{Recompile | encryption | recompile, encryption}
Recompile indicates that SQL server does not cache the plan of the process, and the process will be re-compiled at runtime. Use the recompile option when you use an atypical or temporary value instead of overwriting the execution plan cached in the memory.

Encryption indicates the entries in the SQL Server encrypted syscomments table that contain the create procedure statement text. Encryption prevents the process from being published as part of SQL Server replication.

Note: During the upgrade, SQL server uses the encryption notes stored in syscomments to recreate the encryption process.

For Replication

The storage process created for replication cannot be executed on the subscription server .. Stored Procedures created using the for replication option can be used for filtering stored procedures and can only be executed during replication. This option cannot be used with the with recompile option.

As

Specifies the operation to be performed in the process.

SQL _statement

Any number and types of transact-SQL statements to be included in the process. But there are some restrictions.

N

Yes indicates that this process can contain placeholders for multiple Transact-SQL statements.

Note

The maximum size of stored procedures is 128 MB.