oracle| Data | database
first, some concepts of relational databases
1, the value of the primary key can not be changed generally
2. Foreign key: A field that points to another table or to the primary key or unique key of this table. The
1. Verify that the database has been successfully installedThe Select status from V$instance status displays the open2. How to return the Oracle database to the operating systemExit3, login Oracle database A total of two authentication
194./* + ordered */
According to the order in which the table appears in from, ordered connects Oracle to the table in this order.
For example:
Select/* + ordered */a. col1, B. col2, C. col3 from Table1 A, Table2 B,
Table3 c Where a. col1 = B. col1
Oracle
Oracle Common Fool question 1000 question (vi)
Author: ccbzzp
There are a lot of things that can come up to you when you're using Oracle, especially for beginners, today I simply end it, and I want to give it to everyone and hope it helps!
201./* + NOCACHE (TABLE )*/When a full table scan is performed, the CACHE prompts that the retrieval block of the table can be placed in the nearest least recently used LRU list in the buffer CACHE.For example:SELECT/* + FULL (BSEMPMS) NOCAHE
204. How do I obtain the ASCII value of the first character of a string?
ASCII (char)
Select ASCII ('abcde') from dual;
Result: 65
205. How do I get the characters specified by data value n?CHR (N)Select CHR (68) from dual;Result: d
206. How to
Here are some basic examples of using regular expressions for MVC routing rules.
/* Front * // The specified id can only be a number and the length is 0 ~ 11 routes. mapRoute ("Archive", "{user}/Archive/{id}", new {controller = "Blog", action =
---restore content starts---Round formatted numeric values (carry rules adhere to "quad six into five pairs", that is, the previous one is odd, then into one, the former is an even number rounded, therefore, rount (1.5) =2,round (2.5) =2,round (0.15)
Database Knowledge points1. Database operations:Add: INSERT into Table name values (value 1, value 2, value 3)Delete: Delete column name from table name whereConditionsChange: Update table Name set = value whereTable name = valueCheck: SELECT * FROM
1. Title DescriptionEnter an integer n to find the number of occurrences of the decimal representation of the n integers from 1 to n. 1. For example, enter 12, from 1 to 12 these integers contain 1 of the numbers have 1,10,11 and 12, 11 have
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