if not exists

First, let's talk about why the tables are divided.When a piece of data reaches millions of, you spend more time searching for it, and if you have a joint query, I think it's possible to die there. The purpose of the sub-table is to reduce the

mysql-data table Mysql-create table creationTo create a new table in the database, you can use the MySQL CREATE TABLE statement.CREATE table [IF not EXISTS] table_name ( column_list #在 column_list section specifies a list of tables. )

1. Characteristics of the index 1.1 accelerating the retrieval of conditionsThe query slows down as the amount of table data becomes larger, uses the index on the table's criteria fields, quickly navigates to records that might satisfy the criteria,

I. Creating a database (default character set and collation) (1) Create a database[SQL]View PlainCopy mysql> CREATE DATABASE my_db1; Query OK, 1 row Affected (0.00 sec) (2) Because MY_DB1 already exists, create an error

The Web SQL database API is not part of the HTML5 specification, but it is a separate specification that introduces a set of APIs that use SQL to manipulate the client database.The following are the three core methods defined in the specification:

Today is our knowledge of data related to the next day.First, the field type of the database　1. OverviewIn MySQL, the main types of data are three kinds:Digital, character type, time typeThe primary function of the data type is to set the type of

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-uroot-p;//Opening a databaseAdmin Enter passwordShow databases;//queries all of the librariesUse student;//into the corresponding library or tableCreate database database name;//Creating a librarydrop database name;//Delete a libraryCreate

//************************** * Connect MongoDB database **////*************************Format = ("mongodb://User name: password @ Address: Port/default specified database", parameters)$conn = new Mongo ();can be shortened to$conn =new Mongo ();

One sqlite corresponds to the type of PythonTwo examplesImport Sqlite3Def sqlite_basic ():# Connect to DBconn = Sqlite3.connect (' test.db ')# Create cursorc = Conn.cursor ()# Create TableC.execute ("'CREATE TABLE if not EXISTS stocks(date text,

During theuse of mysq L, you may often encounter the following issues: Some operation syntax forgot, how to quickly find? How do I quickly know the range of values for a field type on the current version? What functions are

Reprint please indicate the source, thank http://blog.csdn.net/harryweasley/article/details/46557807The main purpose of this blog is to describe how to save the database files to the phone system files, and can display the names of the provinces and

A database contains one or more schemas, and the schema contains tables, sequences, functions, and so on, and different schemas can contain tables, sequences, functions, and so on with the same name. A pattern is essentially a namespace, just like a

Sql–create Sql–create Database operationCreate Dateabase test;use test;show databases;show CREATE database test;drop database test;Create database if not exists test; table Action use test; Create table user1 (

The following articles mainly describe the creation and deletion of MySQL databases, as well as the detailed parsing of indexes and changing actual table statements. If you are also popular with MySQL databases, you can click the following article

Query is the core of the database. The following describes how to implement Mysql multi-Table query. If you have encountered any problems in Mysql multi-Table query, take a look.Mysql multi-Table query:Copy codeThe Code is as follows:Create table if

NOTE: For the first time in android, call getWritableDatabase or getReadableDatabase to execute the OnCreate () method. If the table does not exist in the database, we recommend that you create the table: we recommend that you add the judgment

There are many ways to store data in iOS, and when you have a large amount of data, preferences, archiving and plist will not meet your needs.You need to use SQLite or CoreData to store the data.Here's how to use SQLite to store dataTo use SQLite,

What is a table? Table: logically, each table in the database contains rows and a list that can be 0 rows, but at least one table must also support index query. What is a table? Table: logically, each table in the database contains rows and a list

1. The steps are:First join the SQLite development Library Libsqlite3.dylib,Create a new or open database,Create a data table,Insert Data,Querying data and printing2, the method of SQLiteSqlite3 *db, database handle, similar to file handle