In order to communicate with the MySQL server, you must have a good command of SQL. For example, when using a program such as a MySQL client, the function is first as a tool for sending SQL statements to the server. Also, if you write a program that uses the MySQL interface provided by the programming language, you must be familiar with the SQL language because you need to send SQL
Communicate with the server in the sentence.
The 1th chapter "MySQL and SQL Introduction" tutorial introduces a lot of MySQL features. This chapter takes a further look at several aspects of MySQL's SQL based on this tutorial. It discusses how to reference the elements of a database, including naming rules and applicability of case-sensitive constraints. It also introduces many of the more important SQL Qinglie Chiu fashionable lip ê decidua 狻, and back ⒈ Tridacna Flex gourmands -hwan Kua pupa stew qinglie Scratch kua qinglie ┕ 夂 poke Miao men ⒌ Flex Kua lai take u filled mace mu Qiang bone dioxins banter some extensions to standard SQL.
SQL features in 3.1MySQL
The MySQL SQL statement can be grouped into several broad categories, as shown in Figure 3-1. In this chapter, we will introduce the top four categories shown in Figure 3-1. Some of the MySQL utilities provide a mechanism for basic command-line interfaces with some SQL statements. For example, Mysqlshow is an interface to the show COLUMNS statement. These equivalent things are also described in the appropriate place in this chapter. Some of the statements not covered in this chapter will be described in other chapters. For example, the GRANT and REVOKE statements that are used to set user permissions are described in the 11th chapter, "General MySQL administration." The reference syntax for all statements is listed in Appendix D, "SQL syntax reference." Also, refer to the MySQL reference Guide (mysqlreference Manual) For additional information, especially for changes made in the latest version of MySQL.
The last section of this chapter describes MySQL's missing features, some other databases that are not available in MySQL. such as child selection, transaction processing, referential integrity, triggers, stored procedures, and views. Does the lack of these features mean that MySQL is not a "real" database system? Some people think so, but according to the author's view, the lack of these functions does not prevent a large number of people to use it. This is probably because, for most applications, the lack of these features doesn't matter. Other occasions where these functions are needed, there are corresponding solutions. For example, missing a cascading deletion means that you might need to publish an extra query when you delete a record from a table. If you find the use of L O C K
Tables and Unlock tables, the MySQL feature that divides the statements into non-disruptive execution groups is sufficient, so the lack of transaction support may not have any impact on you. (The real problem here is not a lack of transaction, but an automatic fallback to cancel the failed statement.) If there are applications with complex financial transactions, such as the need to complete the processing of several interlocking statements that must be performed as a group, you may consider using a database with a commit/fallback capability, such as using P O s t g R e S. Some of the missing features will be implemented in the future. For example, MySQL does not support subqueries, but is scheduled in version 3. Given in 2 4, perhaps it has been achieved by the time you read this book.
