我想把我的iPhone应用程序迁移到一个新的数据库版本。由于我没有保存一些版本,我需要检查是否存在某些列名。

这个Stackoverflow条目建议执行选择

SELECT sql FROM sqlite_master
WHERE tbl_name = 'table_name' AND type = 'table'

并解析结果。

这是常见的方式吗?选择呢?


当前回答

     //Called when application is started. It works on Droidscript, it is tested
     function OnStart()
     {
     //Create a layout with objects vertically centered. 
     lay = app.CreateLayout( "linear", "VCenter,FillXY" );  

     //Create a text label and add it to layout.
     txt = app.CreateText( "", 0.9, 0.4, "multiline" )  
     lay.AddChild( txt );
     app.AddLayout(lay);

     db = app.OpenDatabase( "MyData" )  
  
     //Create a table (if it does not exist already).  
     db.ExecuteSql( "drop table if exists test_table" )
     db.ExecuteSql( "CREATE TABLE IF NOT EXISTS test_table " +  
       "(id integer primary key, data text, num integer)",[],null, OnError )  
        db.ExecuteSql( "insert into test_table values (1,'data10',100), 
        (2,'data20',200),(3,'data30',300)")
        //Get all the table rows.      
        DisplayAllRows("SELECT * FROM test_table");
        DisplayAllRows("select *, id+100 as idplus, 'hahaha' as blabla from 
        test_table order by id desc;") 
     }

//function to display all records 
function DisplayAllRows(sqlstring)  // <-- can you use for any table not need to 
                                //  know column names, just use a *
                                // example: 
{ 
//Use all rows what is in ExecuteSql  (try any, it will works fine)
db.ExecuteSql( sqlstring, [], OnResult, OnError ) 
} 
//Callback to show query results in debug.  
function OnResult( res )   
{  
var len = res.rows.length; 
var s = txt.GetText();  
// ***********************************************************************
// This is the answer how to read column names from table:
for(var ColumnNames in res.rows.item(0)) s += " [ "+ ColumnNames +" ] "; // "[" & "]" optional, i use only in this demo 
// ***********************************************************************
//app.Alert("Here is all Column names what Select from your table:\n"+s);
s+="\n";
for(var i = 0; i < len; i++ )   
{  
    var rows = res.rows.item(i) 
    for (var item in rows) 
        {
            s += "    " + rows[item] + "   ";
        }
    s+="\n\n";
} 
//app.Alert(s);
txt.SetText( s )  
}  
//Callback to show errors.  
function OnError( msg )   
{  
   app.Alert( "Error: " + msg )  
}  

其他回答

当你运行sqlite3命令行时,输入:

sqlite3 -header

也会给你想要的结果吗

我知道这是一个旧的帖子,但最近我需要同样的帖子,并找到了一个简洁的方法:

SELECT c.name FROM pragma_table_info('your_table_name') c;

只是为了像我这样的超级菜鸟想知道人们是如何或什么意思

PRAGMA table_info('table_name') 

你想使用它作为你的准备语句,如下所示。这样做将选择一个与此类似的表,只是填充了属于您的表的值。

cid         name        type        notnull     dflt_value  pk        
----------  ----------  ----------  ----------  ----------  ----------
0           id          integer     99                      1         
1           name                    0                       0

其中id和name是列的实际名称。所以要得到这个值,你需要使用以下命令选择列名:

//returns the name
sqlite3_column_text(stmt, 1);
//returns the type
sqlite3_column_text(stmt, 2);

它将返回当前行的列名。为了获取它们或找到你想要的,你需要遍历所有行。最简单的方法是采用下面的方式。

//where rc is an int variable if wondering :/
rc = sqlite3_prepare_v2(dbPointer, "pragma table_info ('your table name goes here')", -1, &stmt, NULL);

if (rc==SQLITE_OK)
{
    //will continue to go down the rows (columns in your table) till there are no more
    while(sqlite3_step(stmt) == SQLITE_ROW)
    {
        sprintf(colName, "%s", sqlite3_column_text(stmt, 1));
        //do something with colName because it contains the column's name
    }
}

下面的命令设置列名:

.header on

然后,它是这样的:

sqlite> select * from user;
id|first_name|last_name|age
1|Steve|Jobs|56
2|Bill|Gates|66
3|Mark|Zuckerberg|38

下面的命令取消设置列名:

.header off

然后,它是这样的:

sqlite> select * from user;
1|Steve|Jobs|56
2|Bill|Gates|66
3|Mark|Zuckerberg|38

这些命令显示了".header"命令的详细信息:

.help .header

Or:

.help header

然后,它是这样的:

sqlite> .help .header
.headers on|off          Turn display of headers on or off

此外,下面的命令设置输出模式“box”:

.mode box

然后,它是这样的:

sqlite> select * from user;
┌────┬────────────┬────────────┬─────┐
│ id │ first_name │ last_name  │ age │
├────┼────────────┼────────────┼─────┤
│ 1  │ Steve      │ Jobs       │ 56  │
│ 2  │ Bill       │ Gates      │ 66  │
│ 3  │ Mark       │ Zuckerberg │ 38  │
└────┴────────────┴────────────┴─────┘

并且,下面的命令设置输出模式“table”:

.mode table

然后,它是这样的:

sqlite> select * from user;
+----+------------+------------+-----+
| id | first_name | last_name  | age |
+----+------------+------------+-----+
| 1  | Steve      | Jobs       | 56  |
| 2  | Bill       | Gates      | 66  |
| 3  | Mark       | Zuckerberg | 38  |
+----+------------+------------+-----+

这些命令显示了命令".mode"的详细信息:

.help .mode

Or:

.help mode

然后,它是这样的:

sqlite> .help .mode
.import FILE TABLE       Import data from FILE into TABLE
   Options:
     --ascii               Use \037 and \036 as column and row separators
     --csv                 Use , and \n as column and row separators
     --skip N              Skip the first N rows of input
     --schema S            Target table to be S.TABLE
     -v                    "Verbose" - increase auxiliary output
   Notes:
     *  If TABLE does not exist, it is created.  The first row of input
        determines the column names.
     *  If neither --csv or --ascii are used, the input mode is derived
        from the ".mode" output mode
     *  If FILE begins with "|" then it is a command that generates the
        input text.
.mode MODE ?OPTIONS?     Set output mode
   MODE is one of:
     ascii       Columns/rows delimited by 0x1F and 0x1E
     box         Tables using unicode box-drawing characters
     csv         Comma-separated values
     column      Output in columns.  (See .width)
     html        HTML <table> code
     insert      SQL insert statements for TABLE
     json        Results in a JSON array
     line        One value per line
     list        Values delimited by "|"
     markdown    Markdown table format
     qbox        Shorthand for "box --width 60 --quote"
     quote       Escape answers as for SQL
     table       ASCII-art table
     tabs        Tab-separated values
     tcl         TCL list elements
   OPTIONS: (for columnar modes or insert mode):
     --wrap N       Wrap output lines to no longer than N characters
     --wordwrap B   Wrap or not at word boundaries per B (on/off)
     --ww           Shorthand for "--wordwrap 1"
     --quote        Quote output text as SQL literals
     --noquote      Do not quote output text
     TABLE          The name of SQL table used for "insert" mode
PRAGMA table_info(table_name);

会给你一个列有所有列名的列表。