如何使用Java從MySQL獲取列規範？

Question

在MySQL中，每列都有二進制，無符號和Zerofill標誌。有沒有辦法用Java 1.8獲得這個標誌的值？正如我所見，DatabaseMetaData.getColumns（）不返回這個值。

Answer 1

假設一個測試表與

CREATE TABLE tableA 
( id int auto_increment primary key, 
    w INT(8) ZEROFILL NOT NULL, 
    x INT(8) NOT NULL, 
    y int signed not null, 
    z int unsigned not null, 
    shortBinaryCharString char(10) binary not null, 
    myBlob blob(10000) null 
); 

如從here大多借用爲起點產生。

我會建議使用標準查詢在INFORMATION_SCHEMA數據庫中的表。如

select table_schema, table_name, column_name, ordinal_position, is_nullable, data_type, 
character_set_name, collation_name, column_type, column_key, extra 
from INFORMATION_SCHEMA.columns 
where table_schema = 'so_gibberish' -- your database/schema name 
and table_name='tableA' 


+--------------+------------+-----------------------+------------------+-------------+-----------+--------------------+----------------+--------------------------+------------+----------------+ 
| table_schema | table_name | column_name   | ordinal_position | is_nullable | data_type | character_set_name | collation_name | column_type    | column_key | extra   | 
+--------------+------------+-----------------------+------------------+-------------+-----------+--------------------+----------------+--------------------------+------------+----------------+ 
| so_gibberish | tablea  | id     |    1 | NO   | int  | NULL    | NULL   | int(11)     | PRI  | auto_increment | 
| so_gibberish | tablea  | w      |    2 | NO   | int  | NULL    | NULL   | int(8) unsigned zerofill |   |    | 
| so_gibberish | tablea  | x      |    3 | NO   | int  | NULL    | NULL   | int(8)     |   |    | 
| so_gibberish | tablea  | y      |    4 | NO   | int  | NULL    | NULL   | int(11)     |   |    | 
| so_gibberish | tablea  | z      |    5 | NO   | int  | NULL    | NULL   | int(10) unsigned   |   |    | 
| so_gibberish | tablea  | shortBinaryCharString |    6 | NO   | char  | utf8    | utf8_bin  | char(10)     |   |    | 
| so_gibberish | tablea  | myBlob    |    7 | YES   | blob  | NULL    | NULL   | blob      |   |    | 
+--------------+------------+-----------------------+------------------+-------------+-----------+--------------------+----------------+--------------------------+------------+----------------+ 

您還可能有運氣與執行

SHOW FIELDS FROM tableA;

或

show create table tableA

用標準的Java結果集，你最有可能已經在這樣做就足夠了。

try { 
     con = DriverManager.getConnection(url, user, password); 
     st = con.createStatement(); 
     rs = st.executeQuery("show fields from tableA"); 
     while (rs.next()) { 
      System.out.println(rs.getString(1)+": "+rs.getString(2)); 
} catch (SQLException ex) { 
    Logger lgr = Logger.getLogger(myTest.class.getName()); 
    lgr.log(Level.SEVERE, ex.getMessage(), ex); 
} 

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注：字符集，並顯示出對比檢驗列的原因在於，存在具有與某個字符集排序順序炭二進制列之間的細微差別的差別。與沒有二進制排序順序的真正二進制blob/text列相比。請參閱標題爲The BINARY and VARBINARY Types的Mysql手冊頁，並確定它如何適用於「二元」概念。通常，必須解析一列輸出以確定是否打開zerofill。