第二部分字符串函數(shù)
1. ASCII('str'): 返回字符串 str 中最左邊字符的 ASCII 代碼值副硅。
2. BIN(N): 返回十進(jìn)制數(shù)值 N 的二進(jìn)制數(shù)值的字符串表現(xiàn)形式欠拾。
3. BIT_LENGTH(str): 返回字符串 str 所占的位長(zhǎng)度。
4. CHAR(N,... [USING charset_name]): 會(huì)將每一個(gè)參數(shù) N 都解釋為整數(shù)，返回由這些整數(shù)在 ASCII 碼中所對(duì)應(yīng)字符所組成的字符串。
5. CHAR_LENGTH(str): 單純返回 str 的字符串長(zhǎng)度;
6. CONV(N,from_base,to_base): 將數(shù)值在不同進(jìn)制間轉(zhuǎn)換。
7. COMPRESS():壓縮(不推薦使用 CHAR 或VARCHAR 來(lái)存儲(chǔ)壓縮字符串渤愁。最好使用一個(gè) BLOB 列代替);
8. UNCOMOPRESS(): 解壓內(nèi)容
壓縮實(shí)例:
MariaDB[study_db]> SELECT
-> LENGTH(REPEAT('a', 50)),
-> LENGTH(COMPRESS(REPEAT('a',50))),
-> COMPRESS(REPEAT('a',50)),
-> UNCOMPRESS(COMPRESS(REPEAT('a',50)));
+-------------------------+----------------------------------+--------------------------+----------------------------------------------------+
| LENGTH(REPEAT('a', 50)) | LENGTH(COMPRESS(REPEAT('a',50))) | COMPRESS(REPEAT('a',50)) | UNCOMPRESS(COMPRESS(REPEAT('a',50))) ??????????????|
+-------------------------+----------------------------------+--------------------------+----------------------------------------------------+
| ?????????????????????50 | ??????????????????????????????16 | 2 ??x?KL$ ??\? ???????????| aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa |
+-------------------------+----------------------------------+--------------------------+----------------------------------------------------+
1 row in set (0.00 sec)
2.2大小寫(xiě)UPPER()與LOWER()
MariaDB[study_db]> select book_name, book_author_name FROM new_books;
+------------------+---------------------------+
|book_name|book_author_name|
+------------------+---------------------------+
|跟我學(xué)MariaDB|hhw|
|跟我學(xué)NodeJS|hhw|
|HTTP權(quán)威指南|O'Reilly|
|追風(fēng)箏的人|Khaled Hosseini|
MariaDB [study_db]> select UPPER(book_name),LOWER( book_author_name) FROM new_books;
+------------------+---------------------------+
|UPPER(book_name)|LOWER( book_author_name)|
+------------------+---------------------------+
|跟我學(xué)MARIADB|hhw|
|跟我學(xué)NODEJS|hhw|
|HTTP權(quán)威指南|o'reilly|
|追風(fēng)箏的人|khaled hosseini|
|小王子|antoine marie jean-b|
