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?
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
. schema table_name
这将从数据库中列出表的列名。
希望这能有所帮助!!
如果有的话
.headers ON
你会得到你想要的结果。
当你运行sqlite3命令行时,输入:
sqlite3 -header
也会给你想要的结果吗
为了获得列信息,你可以使用下面的代码片段:
String sql = "select * from "+oTablename+" LIMIT 0";
Statement statement = connection.createStatement();
ResultSet rs = statement.executeQuery(sql);
ResultSetMetaData mrs = rs.getMetaData();
for(int i = 1; i <= mrs.getColumnCount(); i++)
{
Object row[] = new Object[3];
row[0] = mrs.getColumnLabel(i);
row[1] = mrs.getColumnTypeName(i);
row[2] = mrs.getPrecision(i);
}
PRAGMA table_info(table_name);
会给你一个列有所有列名的列表。