expression
LOWER Role: to convert a string to uppercase letters lowercase forms, numbers, punctuation marks and special characters remain unchanged. Syntax: LOWER (s) When the data and the date literal as a parameter appears, they will be implicitly converted to cha
Simplify the use of the general function of the column may contain null values. These functions accept all data types of input parameters. NVL function NVL function to assess any data type of column or expression is not empty. If the original item is null
Window function can be calculated within a certain record, within a certain value, or accumulated over time and as well as moving average and so on. The reason to use the term window, because the results of treatment using a sliding range of the query res
8.4 RMAN Command Color RMAN backup as a professional tool, it is almost taking into account the backup and recovery process may encounter a variety of operations, it also offers a variety of commands to facilitate these operations. 8.4.1 show RMAN de ...
The use of NULL value, we must remember that following a few rules to avoid some common mistakes: 1. The comparison value, if empty, then calculated the total for the NULL 2. For null value application logic operator NOT, the result was NULL 3. Condi ...
Variables and constants are in the program or subroutine into the block when they were initialized. By default, variables are initialized as NULL's. Unless we specify a value for the variable, otherwise the result is unknown. See the following ex ...
oracle in exists, and in brief usage description There are two simple examples to illustrate the "exists" and the "in" the efficiency of the 1) select * from T1 where exists (select 1 from T2 where T1. A = T2. A); T1 and T2 a smal ...
690. USER_LOB_PARTITIONS The current user has a sub-partition of the LOB data in the partition-level attributes. 691. USER_LOBS Show the user table contains a LOB. 692. USER_LOG_GROUP_COLUMNS Owned by the current user specified in the column in the l ...
If the SELECT statement are used Alias, DISTINCT operator, expression, SET (union, union all, minus, intersect) operators, , or aggregate (count, max, mix, avg) functions, you can not update query return value ; eg: TABLE: emp id name salary ======== ...
The function of the background process for a brief introduction: DBWR process: the process of implementation of the data files will be written into the buffer zone, buffer storage area is responsible for the management of an ORACLE background process ...
rn rn I. Overview rn Defined in ORACLE8: scalar (SCALAR), composite (COMPOSITE), reference (REFERENCE) and four LOB data types, the following details of their characteristics. rn Second, scalar (SCALAR) rn Legitimate scalar column types and database ...
4. WITH query_name AS (subquery)
22/06/2005 12:22 FP Oracle from 8.1.6 to provide an analysis of the start function, analysis of group-based function used to calculate the value of a polymer, and polymerization of its function is different for each group to return to multi-line, and the
Can type in the operating system to obtain tkprof all available options and output options to sort a list of note has Sort Option Description call analysis prscnt execnt fchcnt the implementation of the number of extraction Analysis of the implementa ...
rn Create and use partition table rn ORACLE years in the event of particularly large table, you can use the partition table to change their application performance. rn Logged to a database system, view the v $ option view, if one of Partition is TRUE ...
5.2.2 Optimizer process In section 2.2.7, we have already optimizer understand the treatment process, where we will further introduction. Database system on the SQL statement handle, go through the following three steps: (1) syntax analysis and trans ...
Rely on, and now because of their work relationship, access to the database, previously did not expect to be dealing with the database, faint. rn Recorded on the blog click on the databases of the more important principle: rn Standardization on the t ...
Always use the to_date function to query the data within a specific time. However, each time re-use someone else's written statement about the date change has been the format of the function of the TO_date not know. Read this book above the to_da ...
When you use SQL language, a query to the database when you release, ORACLE will be produced with an "implementation plan" that is, the statement which data search through the implementation of the program, through full table scan, index se ...
