DB2 API 开发指南：嵌入式SQL应用

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"DB2 API 开发相关文档，包括在Linux, UNIX, 和 Windows上开发嵌入式SQL应用程序的DB2 Version 9指南" 在DB2数据库系统中，API（Application Programming Interface）开发是构建与数据库交互的应用程序的关键部分。本资源主要针对"DB2 API development"，特别是关于在Linux, UNIX, 和 Windows环境下开发嵌入式SQL应用程序的DB2 Version 9指南，这是一份重要的技术文档，编号为SC10-4232-00。 DB2的API提供了丰富的功能，使得开发者能够高效、安全地执行SQL语句，管理数据库事务，以及处理数据查询和更新。其中，嵌入式SQL是一种将SQL语句直接嵌入到主语言（如C, C++或Java）源代码中的编程方式，它允许应用程序直接与数据库进行交互，而无需通过独立的SQL接口。本指南可能涵盖了以下关键知识点： 1. **嵌入式SQL编程基础**：介绍如何在主语言中声明和使用SQL语句，包括声明SQL变量，预编译和执行SQL语句，以及处理结果集。 2. **数据访问和操纵**：详细说明如何使用API来插入、更新、删除和查询数据库中的记录，包括使用游标进行遍历和定位数据。 3. **事务管理**：讲解如何使用API进行事务的开始、提交、回滚等操作，确保数据的一致性和完整性。 4. **错误处理和诊断**：描述了在API调用中如何处理错误，获取错误信息，以及如何进行调试。 5. **性能优化**：可能包含关于如何利用索引、存储过程、批量处理等技术提升应用程序的性能。 6. **连接管理**：介绍如何建立和断开与DB2服务器的连接，以及管理连接池以提高效率。 7. **安全性**：讨论如何设置和管理用户权限，以及使用API进行身份验证和授权。 8. **数据库设计与对象创建**：可能涵盖如何使用API创建和管理表、视图、索引和其他数据库对象。 9. **高级特性**：可能包含对触发器、存储过程、游标的高级用法，以及支持XML、大数据类型等功能的使用。为了充分利用这份资源，开发者应熟悉相关的编程语言，了解SQL语法，并具备基本的数据库理论知识。同时，IBM提供的在线资源，如IBM Publications Center和IBM Directory of Worldwide Contacts，是获取最新文档、技术支持和订购印刷版资料的重要渠道。 DB2 API开发是构建高效、健壮的数据库应用的核心技能，这份文档对于在Linux, UNIX, 和 Windows平台上开发DB2 Version 9应用程序的开发者来说，无疑是一份宝贵的参考资料。

Embedded SQL statements in FORTRAN applications

Embedded SQL statements in FORTRAN applications consist of the following three

elements:

Element Correct FORTRAN Syntax

Statement initializer EXEC SQL

Statement string Any valid SQL statement with blanks as delimiters

Statement terminator End of source line.

The

end of the source line serves as the statement terminator. If the line is

continued, the statement terminator is the end of the last continued line.

For example:

EXEC SQL SELECT COL INTO :hostvar FROM TABLE

The following rules apply to embedded SQL statements in FORTRAN applications:

v Code SQL statements between columns 7 and 72 only.

v Use full-line FORTRAN comments, or SQL comments, but do not use the

FORTRAN end-of-line comment '!' character in SQL statements. This comment

character may be used elsewhere, including host variable declarations.

v Use blanks as delimiters when coding embedded SQL statements, even though

FORTRAN statements do not require blanks as delimiters.

v Use only one SQL statement for each FORTRAN source line. Normal FORTRAN

continuation rules apply for statements that require more than one source line.

Do not split the EXEC SQL statement initializer between lines.

v SQL comments are allowed on any line that is part of an embedded SQL

statement. These comments are not allowed in dynamically executed statements.

The format for an SQL comment is a double dash (--), followed by a string of

zero or more characters and terminated by a line end.

v FORTRAN comments are allowed almost anywhere within an embedded SQL

statement. The exceptions are:

– Comments are not allowed between EXEC and SQL.

– Comments are not allowed in dynamically executed statements.

– The extension of using ! to code a FORTRAN comment at the end of a line is

not supported within an embedded SQL statement.

Use exponential notation when specifying a real constant in SQL statements. The

database manager interprets a string of digits with a decimal point in an SQL

statement as a decimal constant, not a real constant.

v Statement numbers are invalid on SQL statements that precede the first

executable FORTRAN statement. If an SQL statement has a statement number

associated with it, the precompiler generates a labeled CONTINUE statement

that directly precedes the SQL statement.

v Use host variables exactly as declared when referencing host variables within an

SQL statement.

v Substitution of white space characters, such as end-of-line and TAB characters,

occurs as follows:

– When they occur outside quotation marks (but inside SQL statements),

end-of-lines and TABs are substituted by a single space.

8 Developing Embedded SQL Applications

– When they occur inside quotation marks, the end-of-line characters disappear,

provided the string is continued properly for a FORTRAN program. TABs are

not modified.

Note that the actual characters used for end-of-line and TAB vary from platform

to platform. For example, Windows-based platforms use the Carriage

Return/Line Feed for end-of-line, whereas UNIX and Linux based platforms use

just a Line Feed.

Related concepts:

v “Comments in embedded SQL applications” on page 136

v “Concurrent transactions and multi-threaded database access in embedded SQL

applications” on page 27

v “Host variable names in FORTRAN embedded SQL applications” on page 120

v “Restrictions on using FORTRAN to program embedded SQL applications” on

page 25

Related reference:

v “Supported SQL Statements” in Developing SQL and External Routines

Embedded SQL statements in REXX applications

REXX applications use APIs that enable them to use most of the features provided

by database manager APIs and SQL. Unlike applications written in a compiled

language, REXX applications are not precompiled. Instead, a dynamic SQL handler

processes all SQL statements. By combining REXX with these callable APIs, you

have access to most of the database manager capabilities. Although REXX does not

directly support some APIs using embedded SQL, they can be accessed using the

DB2 command line processor from within the REXX application.

As REXX is an interpreted language, you will find it is easier to develop and

debug your application prototypes in REXX, as compared to compiled host

languages. Although database applications coded in REXX do not provide the

performance of database applications that use compiled languages, they do

provide the ability to create database applications without precompiling,

compiling, linking, or using additional software.

Use the SQLEXEC routine to process all SQL statements. The character string

arguments for the SQLEXEC routine are made up of the following elements:

v SQL keywords

v Pre-declared identifiers

v Statement host variables

Make

each request by passing a valid SQL statement to the SQLEXEC routine. Use

the following syntax:

CALL SQLEXEC 'statement'

SQL statements can be continued onto more than one line. Each part of the

statement should be enclosed in single quotation marks, and a comma must

delimit additional statement text as follows:

CALL SQLEXEC 'SQL text',

'additional text',

'final text'

Chapter 1. Introduction to embedded SQL 9

The following is an example of embedding an SQL statement in REXX:

statement = "UPDATE STAFF SET JOB = ’Clerk’ WHERE JOB = ’Mgr’"

CALL SQLEXEC ’EXECUTE IMMEDIATE :statement’

IF ( SQLCA.SQLCODE < 0) THEN

SAY ’Update Error: SQLCODE = ’ SQLCA.SQLCODE

In this example, the SQLCODE field of the SQLCA structure is checked to determine

whether the update was successful.

The following rules apply to embedded SQL statements: in REXX applications

v The following SQL statements can be passed directly to the SQLEXEC routine:

– CALL

– CLOSE

– COMMIT

– CONNECT

– CONNECT TO

– CONNECT RESET

– DECLARE

– DESCRIBE

– DISCONNECT

– EXECUTE

– EXECUTE IMMEDIATE

– FETCH

– FREE LOCATOR

– OPEN

– PREPARE

– RELEASE

– ROLLBACK

– SET CONNECTION

Other SQL statements must be processed dynamically using the EXECUTE

IMMEDIATE, or PREPARE and EXECUTE statements in conjunction with the

SQLEXEC routine.

v You cannot use host variables in the CONNECT and SET CONNECTION

statements in REXX.

v Cursor names and statement names are predefined as follows:

c1 to c100

Cursor names, which range from c1 to c50 for cursors declared without

the WITH HOLD option, and c51 to c100 for cursors declared using the

WITH HOLD option.

The cursor name identifier is used for DECLARE, OPEN, FETCH, and

CLOSE statements. It identifies the cursor used in the SQL request.

s1 to s100

Statement names, which range from s1 to s100.

The statement name identifier is used with the DECLARE, DESCRIBE,

PREPARE, and EXECUTE statements.

The

pre-declared identifiers must be used for cursor and statement names. Other

names are not allowed.

v When declaring cursors, the cursor name and the statement name should

correspond in the DECLARE statement. For example, if c1 is used as a cursor

name, s1 must be used for the statement name.

v Do not use comments within an SQL statement.

Note:

REXX does not support multi-threaded database access.

10 Developing Embedded SQL Applications

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