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In the software testing, the database is the necessary knowledge, holiday busy stealing busy, organized a little study notes, and discuss together.Read CatalogueBasic knowledge History of Database Database nouns SQL composition

first, the data type1, binary type: (with length limit, can put 800 0,1) Format: binary[(n)]--fixed-length n-byte binary data varbinary[(n)]--N-byte variable-length binary data2, character data format:Char[(N)]--fixed-length n character data varchar[

I myself is a beginner of Oracle and SQL, some time ago saw Hanshunping Teacher's Oracle Video tutorial, feel very easy to learn, a lot of harvest. At the same time he also made a lot of notes, now want to put paper notes in their own words summed

First, IntroductionCobar is a distributed storage of data after the product, can support the use of the background of MySQL or Oracle database, through the configuration, the data in accordance with a certain rules stored in different databases. The

?? A data type is an attribute that specifies the type of data that an object can hold, and supports multiple data types in SQL Server, including character types, numeric types, and date types. The data type is equivalent to a container, the size of

A data type is an attribute that specifies the type of data that an object can hold, and supports multiple data types in SQL Server, including character types, numeric types, and date types. The data type is equivalent to a container, the size of

Decimal exact numeric typeThe decimal data type can be used to store numeric data of a fixed precision and range from 10 to 38 powers-1 to 10 of 38 power-1. When you use this data type, you must specify the range and precision. The range is the

First, the basic conceptThe mysql5.1 version begins with the introduction of the event concept. Event is not only a "time trigger", unlike the events triggered by the triggers, the event is similar to a Linux crontab scheduled task for time

Constraints are used to restrict the type of data that is joined to a table.You can specify constraints (through the CREATE TABLE statement) When you create the table, or you can (via the ALTER table statement) after the table is created.We will

One. Common MySQL command-line commands1. Start MySQL service net start MySQLStop MySQL service net stop MySQL 2. Netstat–na | findstr 3306 View the port being monitored, findstr is used to find out if there is a port in the back3. Log in to the

This article contains the following content:1. Oracle PL/SQL usage2.5 Constraints in Oracle (non-NULL constraints, UNIQUE constraints, PRIMARY KEY constraints, FOREIGN KEY constraints, check constraints)3, Oracle single quotation mark, double

Go from source Oracle Long type why not recommended is not deprecated, is generally not used, and sometimes will be used, so can not generalize. 1, a Long data type is stored in a variable length string, the maximum length limit is 2GB. 2,

1. mysql Common commandsCreate database name; Create a databaseUse DatabaseName; Select DatabaseDrop database name deletes databases directly and does not alertShow tables; Show TableDescribe TableName; Detailed description of the tableSELECT * FROM

Because the project needs to create a timer (EVEVT), so Baidu a bit, found that the basic is from a template, some functions are not complete, now summarize their own. Note: The MySQL version is supported for event starting from 5.1. If your version

MySQL Database Common Commands1. mysql Common commandsCreate database name; Create a databaseUse DatabaseName; Select DatabaseDrop database name deletes databases directly and does not alertShow tables; Show TableDescribe TableName; Detailed

same Show The timestamp column is displayed in the same format as the datetime column. In other words, the display width is fixed at 19 characters, and the format is Yyyy-mm-dd HH:MM:SS. different Range datetime Retrieves and displays datetime

SELECT: QuerySELECT select-list from TB WHERE qualification find corresponding rows based on standard qualificationQuery Statement type: Qualification condition Field field distinct uniqueSimple query:Multi-Table query:Sub-query:SELECT * FROM

For composite indexes: MySQL left-to-right uses fields from the index, and a query can use only one part of the index, but only the leftmost section. For example, the index is key index (A,B,C). can support a | a,b| A,b,c 3 combinations to find, but

First, create a data table: The syntax and usage of this command is basically the same as most relational databases, so let's demonstrate the various rules for creating tables in SQLite as an example. But for some sqlite-specific rules, we will give

DDL: Data Definition languageCREATEAlterDROPThe main operations focus on databases and tables.Database:To create a database:CREATE datebase| SCHEMA [IF not EXISTS] dbnane [create_specification];Create_sepecification[DEFAULT] CHARACTER Set [=]