SQL series (basic)-preface supplementary knowledge before class

Preface supplement knowledge before classNumber (p, s)Number (p, s): Number type. p indicates the effective length of the Number (from the left 1st digits of the Number not 0Until the rightmost length. value range: 0 ~ 38 digits), and s indicates

MySQL old and new versions ORDER

MySQL's order by involves three parameters:A. sort_buffer_size sort cache.B. read_rnd_buffer_size second sorting cache.C. max_length_for_sort_data has the maximum sorting constraint for normal columns.Let me briefly describe the sorting rules of

ORA-12545: Connect failed because target host or object does not exist

[Oracle @ ybdbtest oradata] $ sqlplus/nologSQL * Plus: Release on Thu Jun 26 10:16:29 2014Copyright (c) 1982,200 2, Oracle Corporation. All rights reserved. SQL> conn/as sysdba ERROR:ORA-12545: Connect failed because target host

Let you know software development in advance (31): begin and end in database scripts

Part 1 Database SQL language Begin and end in database scripts   In database scripts, begin and end are a strange word. Without them, some code looks confusing; adding them makes the structure of the Code instantly clearer. Indeed, begin and end are

OR less union data is rewritten

SQL> SELECT deptno FROM emp WHERE mgr = 7698 OR job = 'salesman' ORDER BY 1; DEPTNO ---------- 30 30 30 30 30SQL> SELECT deptno FROM emp WHERE mgr = 7698 2 UNION 3 SELECT deptno FROM emp WHERE job = 'salesman' 4 order by 1; DEPTNO ---------- 30SQL>

Sort arrays by PostgreSQL

PostgreSQL supports arrays, but does not have a function to sort internal data elements. Today I wrote one with PLPGSQL and PLPYTHONU respectively.Example Table Structure: t_girl=# \d test_array; Table "ytt.test_array"

ORACLE takes the start time and end time of the week, month, quarter, and year.

 1: Obtain the start time and end time of the week. Start Time of the week, starting from Monday. SQL> SELECT TRUNC (TO_DATE ('2017-11-25 10:31:11 ', 'yyyy-MM-DD HH24: MI: ss'), 'D') + 1 ASA FROM DUAL; A -----------   End Time of the week,

Example of the external data experiment (1) Verify the synchronization between TCUSTMER and TCUSTORD

Continue with "golden Data configuration (4)": Click to open the link Example of the external data experiment (1) Verify the synchronization between TCUSTMER and TCUSTORD Environment: Item Source System Target System

QlikView arbitrarily changes the legend position

The team spent a lot of money asking people to design a set of UI solution, but it was a report style designed based on the website idea. However, the uidesign Team of the report did not have the background of QlikView, therefore, I don't know

Summary of advantages and disadvantages of five ORACLE tables

Summary of the advantages and disadvantages of the five ORACLE tables:1. Normal table: Suitable for most design scenarios, with advantages and disadvantages.Advantages:A. The syntax is simple and convenient.B. Suitable for most

RMAN-05537: DUPLICATE without TARGET connection when auxiliary instance is started with spfile canno

Today is. the following error occurs when copying data: RMAN-05537: DUPLICATE without TARGET connection when auxiliary instance is started with spfile cannot use SPFILE clause The procedure is as follows: [oracle@dg1 dbs]$ rman target sys/root@dg1

Changing SQL rewrite or to union causes more non-equivalent data

Select count (*) from (select. * FROM (select cd. *, nvl (CV. SUM_CI_BALANCE, 0) as SUM_CI_BALANCE, nvl (CV. SUM_LN_BALANCE, 0) as SUM_LN_BALANCE FROM OCRM_F_CI_CUST_DESC CD left join (select cust_id, FR_ID, sum (CI_BALANCE) as sum_CI_BALANCE, sum

MongoDB one-to-multiple link Modeling

This blog is translated from: Http://blog.mongodb.org/post/87200945828/6-rules-of-thumb-for-mongodb-schema-design-part-1? Mkt_tok = 3RkMMJWWfF9wsRonsq7Ldu % 2FhmjTEU5z14uUsUKGxhokz2EFye % 3D % 3D Note: This translation is not strictly translated. It

Oracle 11g logon Analysis in different situations

This blog has participated in the 2014 CSDN blog contest, if you think this article is useful to you, please move a small hand to help me vote: http://vote.blog.csdn.net/Article/Details? Articleid = 32939867, thank you. For Oracle beginners and

Create a primary key (example)

Create a primary key (example) SQL> alter table emp_ogg add constraint PK_empno primary key (empno ); -- Create a primary key Queries the constraints of a table.SQL> desc user_constraints;   Name Null? Type ---------------------------------------

[DB] basic concepts of HBase

What is Hbase?Before talking about Hase, let's take a look at two concepts: Row-oriented storage and column-oriented storage. For row-oriented storage, I believe everyone should know that the RDBMS we are familiar with is of this type. Row-oriented

[MySQL learning] OUT of range value for column and DATA truncated for column corresponding to STRICT_ALL_TABLES

Yesterday, the insert into a select from B statement was used in the stored procedure. When the bigint field is inserted into the int field in the application, the value is truncated. The inserted value is no longer the expected value. Because

[Oracle] Golden Gate

Golden Gate (OGG for short) provides real-time capturing, conversion, and delivery of transaction data in heterogeneous environments. OGG supports the following heterogeneous environments: OGG features: Small impact on the production system:

Use the DataGridView to add, delete, modify, and query data and synchronize data to the database.

DataGridViewControls are highly configurable and scalable. It provides a large number of attributes, methods, and events that can be used to customize the appearance and behavior of the control. The following example shows how to add, delete, modify,

Let you know about software development in advance (30): blank lines and spaces in database scripts

Part 1 Database SQL language Empty rows and spaces in database scripts     In database scripts, empty rows and spaces play the "icing on the cake" role. Using them appropriately can improve the Code standardization and readability, and thus improve

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