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  SQLite database commonly used sentences and visualization tools on MAC MeasSQLlite use
     
  Add Date : 2018-11-21      
         
         
         
  SQLite is an open source embedded relational database, which is very small, simple and rapid characteristics readily applied to mobile application data management.

One. Introduction

In mobile development, it is common to use some small database for data management. SQLite is a very compact and convenient database in iOS development, its original framework also have very good support.

Two, SQLite common statement

Database meaning of existence lies in its integration and data management, the core operation of the database is nothing more than increase the data, delete, change, Richard operation.

1. Establish a data table statement

A database file may consist of a number of tables, create a table in a database file with the following statement:

create table class (num integer PRIMARY KEY, name text NOT NULL DEFAULT "1 class", count integer CHECK (count> 10))

The above statement code can be simplified into the following formats:

create table table name (the name of a type parameter modification conditions, parameter names 2, Type parameter modification, ...)

sqlite support the following types:

Short Integer smallint

integer integer

real real type

float single-precision floating point

double double-precision floating-point

currency long integer

char varchar

text string

binary binary data

blob blob

boolean boolean

date Date type

time time type

timestamp timestamp type

About modification of the condition, commonly used are the following:

PRIMARY KEY: When this parameter is the primary key value of the primary key must be unique, it can be used as index data, such as numbers.

NOT NULL: This parameter is non-empty tag attributes.

UNIQUE: The only key values of this parameter markers, similar to the primary key.

DEFAULT: the default setting of the parameter

CHECK: Check the condition of parameters, such as the above code, the data is written to count must be greater than when active.

2. Add data

Use the following statement to add rows of data operations:

insert into class (num, name, count) values (2, "three-year 2 classes," 58)

The above statement code can be simplified into the following formats:

insert into table (key 1, key 2, ...) values (value 1, value 2, ...)

Use the following statement to add a column of data, namely, to add a new key:

alter table class add new text

alter table table name add keys Key Type

3. Modify the data

Use the following statement to change the following:

update class set num = 3, name = "new class" where num = 1

update table set key value 1 = 1, 2 = value 2 where key conditions

Modify the data added to the end where conditions such as described above for the modified code num mun names and values of class 1.

4. Delete Data

delete from class where num = 1

delete from table where conditions

The above code deletes num is a 1 data.

To delete a table applicable to the following statement:

drop table class

drop table table name

5. query operation

Query operation is a core function of the database, sqlite many query can quickly perform complex queries.

Some key lookup table:

select num from class

select keys, key ... from table

Discover all key data:

select * from class

select * from table

* Is a full wildcard for any number of characters is not limited

Sort query:

select * from class order by count asc

select keys, key, ... from table name order by sort keys

order by writing back to sort of the key name, there is sort asc desc descending ascending

Find the number of data and find the location restrictions:

select * from class limit 2 offset 0

select keys from table limit the maximum number of queries starting position offset

Criteria query:

select * from class where num> 2

select keys from table where conditions

Query data number:

select count (*) from class

select count (key name) from table

To re-query:

select distinct num from class

select distinct keys from the table name

Three, MesaSQLite simple to use

MesaSQLite is a visual SQLite database editing software, easy to use. Download link following address: http: //pan.baidu.com/s/1skunNOx.
     
         
         
         
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