Data storage--sqlite Database storage

I. Features

1. Storage of data with a certain structure

2. File type. db

Two. SQLite database

1. Features

1-Lightweight relational database

2-Supports multiple programming languages

3-Suitable for use on mobile devices

4-Small installation files

5-Supports multiple operating systems

6-Fast running speed (low data volume)

7-The database itself is a single file

2. Data type

1-integers: INT, integer;

2-floating point: float, DOUBLE;

3-string literal

①char, fixed-length string;

②warchar, variable-length string;

③text, large text;

4-Time: Date, DateTime;

5-File: BLOB, infrequently used, affects query efficiency.

3. Table

N-Table name

2-field

① field name, with English letters and numbers, underline combination;

② Data types

③ data length: Floating-point number, total length or length after decimal point;

④ Default Value

3-Constraints

① non-null constraint: The field contents cannot be null;

② PRIMARY KEY constraints

1> Features

⑴ field content is not empty

⑵ primary key field content (Multi-field content merge) Unique, cannot have duplicate rows

⑶ A table can have only one primary key, but may have more than one primary key field

⑷ commonly used for data retrieval positioning and sorting

2> selection Form

⑴ Unique code information for table data

⑵_id

? auto-Grow field or sequence (self-growing number)

? data type is integral type

? The default is automatically incremented from 1, plus 1 for each fetch

⑶ a string of letters and numbers that uniquely identifies the guid:32 bit globally.

The process of the table:

Data storage--sqlite Database storage