sql in 10 minutes

* from emp WHERE empno = ' 7369 ' 9. Sorting Avoid the use of resource-intensive operations, SQL statements with Distinct,union,minus,intersect,order by will start the SQL engine execution, resource-intensive sequencing ( SORT) feature . DISTINCT requires a sort operation , while others need to perform at least two sorting Temporary Tables Careful use of temporal table can greatly improve t

Organizing data in a meaningful way may be a challenge. Sometimes you may need a simple sort, but you usually need to do more, you need to group for analysis and statistics. Fortunately, SQL provides a large number of statements and operations for sorting, grouping, and summarization. The following tips help you identify when to sort, when to group, and when and how to count. For more information about each statement and operation, see books online.1.

The hints adjustment mechanism used by Oracle has been very complex. Oracle Technical Network has a good overview of the process of using hints to adjust Oracle SQL. According to the introduction of 10 Gb database, more new optimizer hints can be used to control optimization behavior. Now let's take a quick look at these powerful new hints: Spread_min_analysis With this hint, you can ignore the Compilation

Today, we can see a great deal on the new customer network. Article It is about SQL sorting, grouping, and Statistics skills! Let's share it with you! Haha 1. Sort data in order Generally, all of your data really needs to be arranged in a certain order. The SQL order by statement can organize data in alphabetical or numerical order. Therefore, similar values are sorted by group. However, the sorting re

*60)), if not required so accurate, can be omitted this step. 7. The law of the WHERE statement 7.1 Avoid using in,not in,or or having in the WHERE clause. You can use exist and not exist instead of in and not. You can use table links instead of exist. Having can be replaced by where, if not replaced, can be handled in two steps. Example (SELECT customer_name from CUSTOMER) Optimization (SELECT customer_name from CUSTOMER) 7.2 Do not de

it is very important to choose the most appropriate data type, for example, give you 10 18-bit full digital ID number, and 10 15-bit full digital ID card number. Let you find the fastest query speed, these 20 records, then you design this field, there should be a few places to note:1. The fastest query speed, nothing more than we choose int type of data to store these 20 ID numbers. However, the 15-bit and

31. Forced index failure If two or more indexes have the same level, you can force the ORACLE optimizer to use one of them (using it, the number of retrieved records is small ). Example: SELECT ENAME FROM EMP Where empno = 7935 And deptno + 0 = 10/* DEPTNOThe index on will be invalid */ AND EMP_TYPE | ''= 'A'/* EMP_TYPEThe index on will be invalid */ This is a very direct way to improve query efficiency, but you must consider this strategy with c

1. Use sort to make data orderlyTypically, all your data really needs is in some sort of order. An ORDER BY statement of SQL can organize data in alphabetical or numerical sequence. As a result, similar values are sorted together by group. However, the result of sorting in this group is not really a grouping. An order by displays each record and grouping may represent many records. 2. Remove duplicate values by groupingThe biggest difference between

10.1 Manage login AccountCreate login account Syntax format:sp_addlogin login ID, login password, default database, default language, security code, encryptionIn the whether encryption option, NULL indicates encryption of the password. Skipencryption indicates that the password is not encrypted. Skipencryptionold, used only for SQL Server upgrades, indicates that the old version has been encrypted with the password.To modify the login account syntax f

better when your table has fewMillions record and a few lousy queries. (It might not even requiredMillions of hit to kill it)Don't use fast or reliable Disk Using something like a single disk or mirror will definitely makesYour I/O the main bottleneck on your system. With the help of a singleDisk, you can perform ct OS and your database fighting for resources,Serving one user at a time while others waiting for their turn. To makeThings worst, you can try utilize raid-5 instead of RAID-

(I said it was a 10-minute entry. In fact, for me, it was really just the ten minutes that the teacher talked about. It wasn't too exaggerated. Then I knew how to write the stored procedure and trigger, of course it's just getting started, but I have been waiting for ten minutes. It would take at least a few days for me to read a book by myself ....) For a long time, the stored procedures and triggers of SQL