SQLite学习笔记
SQLite学习笔记
（未完成，待修改）
一、无库无表SQL
1. 无库连接sqlite3
(1) Windows提示符
>sqlite3
SQLite version 3.6.22
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite>
(2) adb shell（模拟器或手机）
>adb shell
# sqlite3
sqlite3
SQLite version 3.6.22
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite>
2. 计算字段（通过运算符计算得到的字段，不存在于实际表中）
(1) 常量
sqlite> select 1;
1
(2) 四则运算
sqlite> select 3 + 4, 3 - 4, 3 * 4, 3 / 4, 3 % 4;
7|-1|12|0|3
sqlite> select 3 + 4 * 2;
11
sqlite> select (3 + 4) * 2;
14
sqlite> select -(1+0), +(2+0), ~(2+0);
-1|2|-3
sqlite> select -("hello"), +("hello"), ~("hello");
0|hello|-1
(3) 别名（导出列），相当于临时变量的赋值。
sqlite> select 3 * result, 2 + result from (select 2 as result);
6|4
(4) 拼接（相当于MySQL的Concat()）
sqlite> select 'hello' || ' ' || 'world!';
hello world!
sqlite> select 3 || 1;
31
sqlite> select LTrim(' hello') || RTrim(' world! ');
hello world!
(5) 算术比较与逻辑与或运算
sqlite> select 3 > 2, 3 < 2, 3 = 3, 3 == 3;
1|0|1|1
sqlite> select 1 != 0, 1 <> 0;
1|1
sqlite> select 1 is null, 1 is not null;
0|1
sqlite> select null is null, null is not null, null == null, null != null;
1|0||
sqlite> select (null == null) is null;
1
sqlite> select length(null) is null;
1
sqlite> select 1 = 1, 1 == 1;
1|1
sqlite> select 3 between 4 and 5, 4 between 4 and 5;
0|1
sqlite> select 4 in (1, 3, 4), 0 in (1, 3, 4), 2 not in (1, 3, 4);
1|0|1
sqlite> select (1 >= 2) and (1 <= 3), (1 >= 2) & (1 <= 3);
0|0
sqlite> select (1 < 2) or (1 > 3), (1 < 2) | (1 > 3);
1|1
sqlite> select 1 < 2, not (1 < 2);
1|0
sqlite> select case when 1 > 2 then 3 else 4 end;
4
sqlite> select case 2 when 1 then 3 else 4 end;
4
(6) 使用通配符的字符串匹配（MySQL没有glob。like通配符：%匹配0个或0个以上字符，_匹配1个字符，大小写不敏感；glob通配符：大小写敏感）
sqlite> select 'hello' like 'ell', 'hello' like 'ell%', 'hello' like '%ell%', 'hello' like 'he%', 'hello' like 'h%o';
0|0|1|1|1
sqlite> select 'hello' like '_ello', 'hello' like 'hel_';
1|0
sqlite> select 'Apple' like 'apple', 'Apple' like 'AppL_';
1|1
sqlite> select like('Apple', 'apple');
1
sqlite> select like('App%', 'apple');
1
sqlite> select 'hello' glob 'he*', 'hello' glob 'hell?';
1|1
sqlite> select glob('he*', 'hello'), glob('hell?', 'hello');
1|1
(7) 使用正则表达式的字符串匹配（默认sqlite不实现REGEXP用户函数）
sqlite> select 'a' REGEXP '^a$';
Error: no such function: REGEXP
3. 使用数据处理函数的计算字段（通过函数计算得到的字段，不存在于实际表中）
(1) 文本处理（MySQL使用SubString，不支持MySQL的Soundex()，Left()，Right()，Locate()）
sqlite> select str, Upper(str), Lower(str), Length(str) from (select 'Hello, World!' as str);
Hello, World!|HELLO, WORLD!|hello, world!|13
sqlite> select str, LTrim(str), RTrim(str), Trim(str) from (select ' Hello, World! ' as str);
Hello, World! |Hello, World! | Hello, World!|Hello, World!
sqlite> select str, LTrim(str, 'x'), RTrim(str, 'x'), Trim(str, 'x') from (select 'xxxHello, World!xxx' as str);
xxxHello, World!xxx|Hello, World!xxx|xxxHello, World!|Hello, World!
sqlite> select soundex('Y. Lie');
Error: no such function: soundex
sqlite> select SubStr('Hello, World!', 2, 3);
ell
sqlite> select SubStr('Hello, World!', -1, 4);
!
sqlite> select SubStr('Hello, World!', 2, -2);
H
(2) 日期与时间处理（MySQL使用Now()）
sqlite> select DateTime('now');
2012-05-07 05:34:36
sqlite> select strftime('%s', 'now');
1336369355
(3) 数值处理（MySQL使用Rand()，不支持MySQL的Sin()，Cos()，Tan()，Exp()，Mod()，Pi()，Sqrt()）
sqlite> select Abs(-1.2);
1.2
sqlite> select random();
1872328235102936735
(4) 聚集函数（只有Min()和Max()可用于不同列，AVG()，COUNT()，SUM()则不可以用在这里）
sqlite> select min(5, 6, 7), max(5, 6, 7);
5|7
(5) like()与glob()的字符串匹配
见前，略。
（TODO：）
X：其它：
(8) 全文搜索和MATCH（MySQL则需要用FULLTEXT()在CREATE TABLE中指定列，用Match()指定被搜索列，用Against()指定表达式）
>sqlite3 test2.sqlite
SQLite version 3.6.22
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> .tables
sqlite> CREATE VIRTUAL TABLE mail USING fts3(subject, body);
sqlite> .tables
mail mail_content mail_segdir mail_segments
sqlite> INSERT INTO mail(docid, subject, body) VALUES(1, 'software feedback', 'found it too slow');
sqlite> INSERT INTO mail(docid, subject, body) VALUES(2, 'software feedback', 'no feedback');
sqlite> INSERT INTO mail(docid, subject, body) VALUES(3, 'slow lunch order', 'was a software problem');
sqlite> SELECT * FROM mail WHERE subject MATCH 'software';
software feedback|found it too slow
software feedback|no feedback
private void setPragmaCacheSize(Connection connection) {
Statement s = null;
try {
s = connection.createStatement();
s.execute("PRAGMA cache_size = " + DB_CACHE_SIZE + ";");
} catch (SQLException e) {
LogUtil.error(logger, "PRAGMA cache_size error", e);
} finally {
try {
if (s != null) {
s.close();
}
} catch (SQLException e2) {
e2.printStackTrace();
}
}
}使用：con = DriverManager.getConnection(url); setPragmaCacheSize(con);
（TODO：）