Question

我想知道在SQLite中检查列和索引是否有一个很好的IF NOT EXISTS，或者我是否需要恢复整个数据库模式并对其进行验证？

Answer 1

您可以使用名为sqlite_master的系统目录表来检查索引（或其他）名称：

SELECT name FROM sqlite_master WHERE type='index' ORDER BY name;

您可以使用pragma获取索引列：

PRAGMA index_info(index-name);

这个用于获取表的列名：

PRAGMA table_info(table-name);

Answer 2

是的，sqlite支持以下语法：CREATE INDEX IF NOT EXISTS ...

See here

要检查列的存在，您可以尝试执行SELECT col from TABLE之类的操作。如果它没有返回错误，则表格中包含col。

Answer 3

在SQLite中，如果你想检查你的列中是否存在列/字段....试试这个答案对我有用... https://stackoverflow.com/a/28146506/3126569

Cursor res = db.rawQuery("PRAGMA table_info("+tableName+")",null);
int value = res.getColumnIndex(fieldName);

Answer 4

我就是这样做的，

INSERT  INTO AUDITEVENT (CODE, DESCRIPTION, AUDITEVENTPK)  
SELECT 'value1', 'value2', 'value3' 
WHERE NOT EXISTS (SELECT 1 FROM AUDITEVENT WHERE CODE = 'value1')

在我的IDConneciton中，我有一个名为ProcessCommandText的方法，用于将查询从SQL Server语法更新为仅SQLite。

这是该方法的实现

public string ProcessSqlText(string text)
{
    var result = text.Replace("SET ANSI_NULLS ON", "").
            Replace("SET ANSI_NULLS ON", "").
            Replace(" ASC)", ")").
            Replace("TOP 100", "TOP(100)").
            Replace("TOP 1", "TOP(1)").
            Replace(" VARCHAR", " NVARCHAR").
            Replace(" CHAR", " NCHAR").
            Replace(" TEXT", " NTEXT").
            Replace("WITH ( IGNORE_DUP_KEY = OFF)", "").
            Replace("SET QUOTED_IDENTIFIER ON", "").
            Replace("SET ANSI_PADDING ON", "").
            Replace("SET ANSI_PADDING OFF", "").
            Replace("SET ANSI_WARNINGS ON", "").Trim(' ').
            Replace("WITH NOCHECK", "").
            Replace("(nolock)", "").
            Replace("CREATE CLUSTERED INDEX", "CREATE NONCLUSTERED INDEX").
            Replace("CREATE UNIQUE CLUSTERED INDEX", "CREATE UNIQUE NONCLUSTERED INDEX").
            Replace("[dbo].", "").
            ToUpper().
            Replace("NEWID()", "'" + Guid.NewGuid().ToString() + "'"). // NEWID() is not supported
            Replace("GO", ""); // GO is not supported


    if (result.Contains("TOP(100)"))
    {
        result = result.Replace("TOP(100)", "");
        result += " LIMIT 100";
    }
    if (result.Contains("TOP(1)"))
    {
        result = result.Replace("TOP(1)", "");
        result += " LIMIT 1";
    }
    if (result.Contains("DATEPART"))
    {
        result = result.Replace("DATEPART", "strftime");
        result = result.Replace("minute", "'%M'");
        result = result.Replace("day", "'%d'");
        result = result.Replace("month", "'%m'");
        result = result.Replace("year", "'%Y'");
    }

    result = TransformIfNotExistsQueriesToSqlLite(result);
    return result;
}

private string TransformIfNotExistsQueriesToSqlLite(string query)
{
    var ifNotExistsRegEx = @"(IF NOT EXISTS\s+)\(+.+\)+\r+\n+INSERT+";
    var m = Regex.Match(query, @"(IF NOT EXISTS\s+)\(+.+\)+\r+\n+INSERT+", RegexOptions.IgnoreCase);

    if (m.Groups.Count > 0 && m.Groups[0].Value.Contains("IF NOT EXISTS"))
    {
        var conditionalStatement = m.Groups[0].Value;
        var newQuery = query.Replace(conditionalStatement, " INSERT ");
        conditionalStatement = conditionalStatement.ToUpper().Replace("IF", "WHERE").Replace("INSERT", "");

        newQuery = Regex.Replace(newQuery.ToUpper(), @"VALUES\s+\(+", " SELECT ");
        var lastIndexOfClosingBracket = newQuery.LastIndexOf(')');
        newQuery = newQuery.Substring(0, lastIndexOfClosingBracket);
        return newQuery + " " + conditionalStatement;   
    }
    return query;
}

Answer 5

为什么不抓住异常？例如：

try{
    db.execSQL("ALTER TABLE ACCOUNT_ENTRY ADD COLUMN ID_CONCEPT NUMBER(10)");
}catch(Exception e){
    System.out.println(e);

}

SQLite如果列存在

5 个答案: