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New API features JDK 6 provides an API for calling the compiler at runtime. We will assume that this API is applied to JSP technology later. In traditional JSP technology, the following six steps are usually required for servers to process JSP:

Mysql -- SQL Optimization-count the number of Certain types and the number of mysqlsql Optimizations Sometimes we want to count the number of such SQL statements. In addition to full table scanning, filesort takes 1.34 seconds. mysql> select

A stored procedure is a program stored in a database (just like a subroutine in a regular language). To be precise, MySql supports two types of "routine (routine: one is the stored procedure, and the other is the function that can return values in

Use the explain statement to check optimizer action +----+-------------+----------+-------+---------------+------+---------+------+------+------- ---------- | ID | Select_type | Table | Type | Possible_keys | Key | key_len| Ref | Rows | Extra +----+-

I. Grammar Explain For example: Explain select * from T3 where id=3952602; Two. Explain output interpretation The code is as follows Copy Code +----+-------------+-------+-------+-------------------+---------+--------

MySQL tutorial sexplain syntax and usage Explain [extended] select ... from ... where ... If extended is used, then after the explain statement is executed, you can use the show warnings statement to query the corresponding Optimization

A stored procedure is a program stored in a database library (like a subroutine in a regular language), and, to be exact, there are two types of MySQL-supported "routine": one is the stored procedure we say, The second is a function that can return

If you put the keyword explain,mysql in front of the SELECT statement, it explains how it handles the Select, providing an order about how tables are joined and joined.Each output row of the explain provides information about a table, and each row

This example describes Android's approach to acquiring mobile phone numbers based on APN. Share to everyone for your reference. Specifically as follows: Before many people said that can not fully obtain mobile phone number, because there are now

Original: http://www.cnblogs.com/growing/archive/2010/11/19/1881372.html Mobile phone numbers are not all available. Just a part of it can be got. This is because the mobile operator did not write the phone number data to the SIM card. SIM card

About SQLite SQLite is an extension of the embedded SQL Database engine SQLite (SQLite embeddable SQL DB Engine). SQLite is an implementation of the embedded SQL database engine small C language library (c library), implemented a stand-alone,

The method currently described is only used to store some simple data. If you want to store relational data, it will be more efficient to use the database. For example, if you want to store the scores of every student in the school, it's best to use

Joint queries are more efficient, with examples to illustrate Federated queries: The benefits and usage of inline inner join, leftist left outer join, right-outer JOIN, full-union, fully outer join.The efficiency of joint queries is high, and the

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1. The test data is as follows:Sql> select * from T1;A | B | C---+----+---1 | 10 | 12 | 20 | 23 | 30 | 34 | 40 | 45 | 50 | 56 | 60 | 6(6 rows)Sql> select * from T2;A | B | D---+----+---1 | 10 | 12 | 20 | 23 | 30 | 3(3 rows)2. Parse the example SQL

Sometimes we want to figure out how many of the types there are and will use this SQL. Full-scale scanning, but also filesort, time-consuming 1.34 seconds.Mysql> Select Country,count (*) from T1 GROUP by country;+---------+----------+| Country |

In the daily work, we will sometimes slow query to record some long-running SQL statements, to find out these SQL statements does not mean that it is done, we often use the explain command to view the execution plan of these SQL statements, to see

1, the use of the deposit process, a lot of similarity to delete, update, new and other operations became easy, and later also easy to manage! 2, stored procedures because the SQL statement has been pre-programmed Yi, so the speed of the run is

RSA typically has two scenarios:1, public key encryption, private key decryption: This is the most common situation in the field of data security communication;2, private key verification, public key check: This is mainly used for digital

Most SQL database engines (as far as we know, all SQL database engines except SQLite) use strict static types. With a static type, the type of the value is determined by its container-the specific column in which the value is stored. SQLite uses a