SQLite basis -3. Grammar and Data Types

A, SQLite grammar

1. Case Sensitivity

It is worth noting that the focus point, SQLite is not case sensitive , but some commands are case-sensitive, such as: GLOB and glob has different meanings in SQLite years.

2. Comment

SQLite notes and other annotations SQL language is the same, are additional notes. Comments can be added to increase the readability of SQL statements.
SQL comments begin with two consecutive "-" character starts with the content of the latter are annotated. It can be written in any place.
Or you can use the "/ *" Start "* /" end. Comment block.

-- select * from LinkMen;
select * from LinkMen;  -- 在语句后面注释

/*这是注释
这也是*/ select * from LinkMen;

3. SQLite statement

So statements can begin with any keywords, such as SELECT, INSERT, UPDATE, DELETE, etc., so the statement in English semicolon ";" at the end.

-- 创建表
CREATE TABLE table_name(
   column1 datatype,
   .....
   columnN datatype,
);

-- 创建索引
CREATE INDEX index_name ON table_name;

-- 创建触发器
CREATE  TRIGGER trigger_name [BEFORE|AFTER] event_name 
ON table_name
BEGIN
 -- 触发器逻辑....
END;

-- 创建视图
CREATE  VIEW view_name AS
SELECT column1, column2, ...
FROM table_name, ...
WHERE [condition];

-- 提交 语句：
COMMIT;

-- 删除表
DROP TABLE database_name.table_name;

-- 删除索引
DROP INDEX database_name.index_name;

-- 删除视图
DROP VIEW view_name;

-- 插入数据
INSERT INTO table_name( column1, column2....columnN)
VALUES ( value1, value2....valueN);

-- 查询数据
SELECT column1, column2....columnN
FROM table_name;

-- 修改数据
UPDATE table_name
SET column1 = value1, ..., columnN=valueN
WHERE [condition];

-- 删除数据
DELETE FROM table_name
WHERE [condition];

-- GROUP BY分组
SELECT SUM(column_name)
FROM   table_name
WHERE  CONDITION
GROUP BY column_name;

-- HAVING对group by加条件过滤
SELECT SUM(column_name)
FROM   table_name
WHERE  CONDITION
GROUP BY column_name
HAVING (arithematic function condition);

-- IN
SELECT column1, column2....columnN
FROM   table_name
WHERE  column_name IN (val-1, val-2,...val-N);

-- LIKE
SELECT column1, column2....columnN
FROM   table_name
WHERE  column_name LIKE [ PATTERN ];

-- ORDER BY 排序
SELECT column1, column2....columnN
FROM   table_name
WHERE  CONDITION
ORDER BY column_name {ASC|DESC};

Two, SQLite data type

Data type is used to specify a data type attribute of any object. Each column, and each variable expression has an associated data type.

type of data	description
NULL	Value is a NULL value.
INTEGER	Value is a signed integer, stored value in accordance with the size of 1,2,3,4,6 or 8 bytes.
REAL	Value is a floating point value, stored as 8-byte IEEE floating-point numbers.
TEXT	Value is a text string, using the database encoding (UTF-8, UTF-16BE or UTF-16LE) storage.
BLOB	Value is a blob data, stored entirely in accordance with its input.

1. Boolean data type

SQLite no separate Boolean storage class. Instead, the Boolean value is stored as an integer of 0 (false) and 1 (true).

2. Date and Time data type

No single SQLite for storing the date and / or time-based storage, but SQLite able to store the date and time as TEXT, REAL or INTEGER value.

type of data	Date Format
TEXT	Format "YYYY-MM-DD HH: MM: SS.SSS" date.
REAL	The number of days from the beginning of noon 4714 BC November 24 Greenwich time counting.
INTEGER	Counting the number of seconds from 1970-01-01 00:00:00 UTC.