learn sql in 21 days

Day 1 I think ASP. NET is much more difficult than ASP. I hope you will be ready. There are many ways to achieve the same effect, which may be confusing. The ten-day series of tutorials will clearly show a variety of methods, so that everyone can be a little less bumpy. In ASP, almost all users use VB, databases, and SQL and ACCESS. In ASP. NET, the database is still one of the two commonly used languages but the other is C #. It is also a language re

The sixth day of learning php in ten days. Objective: to learn how to add or delete the modified data mysql_query ($ exec). you can execute all the operations with this statement. The difference is that the SQL statement $ exec is added: $ execinsertinto. objective: learn to add, delete, and modify data Mysql_query ($

Previously written 10 days to learn the ASP, 10 days to learn asp.net what, now think about writing a PHP bar, also calculate more complete. PHP Debugging methods I do not say here, outside a lot of articles are introduced, there are many different combinations. I'm here for the moment with the Apache Web server and my

Previously written 10 days to learn the ASP, 10 days to learn asp.net what, now think about writing a PHP bar, also calculate more complete. PHP Debugging methods I do not say here, outside a lot of articles are introduced, there are many different combinations. I'm here for the moment with the Apache Web server and my

1) Press the structure on the right: view the change table structure2) Browse by right: View the data in the table3) Press the right SQL: Execute SQL statement4) Press Insert on right: Insert a row of records5) on the right, clear: Delete all records in the table6) Press DELETE on the right: Delete tableAnother very important feature is import and export. But when we have the program and database, we need t

Previously wrote 10 days to learn ASP, 10 days to learn ASP, and now think about writing a PHP bar, but also a comparison of all. PHP Debugging methods I do not say here, there are many articles are introduced, there are many different combinations. For the time being, I am using Apache Web server and my

Previously wrote 10 days to learn ASP, 10 days to learn ASP, and now think about writing a PHP bar, but also a comparison of all. PHP Debugging methods I do not say here, there are many articles are introduced, there are many different combinations. For the time being, I am using Apache Web server and my

Previously written 10 days to learn the ASP, 10 days to learn asp.net what, now think about writing a PHP bar, also calculate more complete. PHP Debugging methods I do not say here, outside a lot of articles are introduced, there are many different combinations. I'm here for the moment with the Apache Web server and my

10 days to learn the first day of PHP Use Apache Web server and my SQL as Web servers and databases under the php-4.3.3 environment to do a simple build and access view database with phpMyAdmin. Syntax for PHP: 1. Embedding Method: PHP can be a 2. Reference documents: There are two ways to refer to a file: Require and include. Require use methods such as require

increase, the students who have learned SQL Server should be familiar with, for example, we do an online user status record, each modification will be on the original basisSelf-increment $inc The specified value, if the "document" does not have this key, then the key will be created, the following example can be understood.② $set modifierDon't say anything, just the code.This is the "word" created by MongoDB, you remember the first parameter of the U

The ninth day of learning php in ten days. Objective: to learn more, I learned ASP first, so I will find many things to adapt to when I do PHP again. 1. do not miss the semicolon. 2. do not miss the $ learning objective before the variable. note: Because I learned ASP first, I will find many places to adapt when I do PHP again. 1. do not miss a semicolon2. do not miss the $3. do not omit session_start (

two ofModifiers: $inc and $set.① $inc modifier$inc is the abbreviation of increase, the students who have learned SQL Server should be familiar with, for example, we do an online user status record, each modification will be on the original basisSelf-increment $inc The specified value, if the "document" does not have this key, then the key will be created, the following example can be understood.② $set modifierDon't say anything, just the code.This i

21 military rules developed by SQL Server 21 military rules developed by SQL Server If you are in charge of a SQL Server-based project or you have just been in touch with SQL Server, you may have to face some database performance

each row of the NULLable column, resulting in more system overhead during query. In addition, setting columns as NULLable makes encoding complex, because each access to these columns must be checked first. I am not saying that NULLS is the root cause of troubles, although some people think so. I think that if you allow "NULL data" in your business rules, setting the column as NULLable sometimes plays a good role. However, if you use NULLable in a similar case, it's just self-defeating. Custom

is the root cause of troubles, although some people think so. I think that if you allow "NULL data" in your business rules, setting the column as nullable sometimes plays a good role. However, if you use nullable in a similar case, it's just self-defeating. Customername1 Customeraddress1 Customeremail1 Customername2 Customeraddress2 Customeremail3 Customername1 Customeraddress2 Customeremail3 In this case, you need to normalize your table. 18. Do not use the text data type

so. I think that if you allow "NULL data" in your business rules, setting the column as nullable sometimes plays a good role. However, if you use nullable in a similar case, it's just self-defeating. Customername1 Customeraddress1 Customeremail1 Customername2 Customeraddress2 Customeremail3 Customername1 Customeraddress2 Customeremail3 In this case, you need to normalize your table. 　　18. Do not use the text data type whenever possible Do not use text unless you use text to process a large amou

query and slow, it will waste a lot of space if it is not used well. Generally, VARCHAR can better process your data .?Do not use temporary tables?Try not to use temporary tables unless you have. Generally, subqueries can replace temporary tables. Using a temporary table will bring about system overhead. If you program using COM +, it will also bring you a lot of trouble, because the use of COM +DatabaseThe temporary table exists from the connection pool to the end.

the column as nullable sometimes plays a good role. However, if you use nullable in a similar case, it's just self-defeating.Customername1Customeraddress1Customeremail1Customername2Customeraddress2Customeremail3Customername1Customeraddress2Customeremail3In this case, you need to normalize your table.18. Do not use the text data type whenever possibleDo not use text unless you use text to process a large amount of data. Because it is not easy to query and slow, it will waste a lot of space if it

. Customername1Customeraddress1Customeremail1Customername2Customeraddress2Customeremail3Customername1Customeraddress2Customeremail3 In this case, you need to normalize your table. 18. Do not use the text data type whenever possibleDo not use text unless you use text to process a large amount of data. Because it is not easy to query and slow, it will waste a lot of space if it is not used well. Generally, varchar can better process your data. 19. Try not to use temporary tablesTry not to u

CustomerName1 CustomerAddress2 CustomerEmail3 If this happens, you need to standardize your watch. 18, try not to use the text data type Unless you use text to process a large number of data, do not use it. Because it is not easy to query, slow, poor use will also waste a lot of space. In general, varchar can better handle your data. 19, try not to use the temporary table Try not to use temporary tables unless you have to. Generally, subqueries can be used in place of temporary tables. Usi