我想在sqlite数据库中删除或添加列

我正在使用以下查询删除列。

ALTER TABLE TABLENAME DROP COLUMN COLUMNNAME

但它会产生错误

System.Data.SQLite.SQLiteException: SQLite error
near "DROP": syntax error

当前回答

我的解,只需要调用这个方法。

public static void dropColumn(SQLiteDatabase db, String tableName, String[] columnsToRemove) throws java.sql.SQLException {
    List<String> updatedTableColumns = getTableColumns(db, tableName);
    updatedTableColumns.removeAll(Arrays.asList(columnsToRemove));
    String columnsSeperated = TextUtils.join(",", updatedTableColumns);

    db.execSQL("ALTER TABLE " + tableName + " RENAME TO " + tableName + "_old;");
    db.execSQL("CREATE TABLE " + tableName + " (" + columnsSeperated + ");");
    db.execSQL("INSERT INTO " + tableName + "(" + columnsSeperated + ") SELECT "
            + columnsSeperated + " FROM " + tableName + "_old;");
    db.execSQL("DROP TABLE " + tableName + "_old;");
}

辅助方法获取列:

public static List<String> getTableColumns(SQLiteDatabase db, String tableName) {
    ArrayList<String> columns = new ArrayList<>();
    String cmd = "pragma table_info(" + tableName + ");";
    Cursor cur = db.rawQuery(cmd, null);

    while (cur.moveToNext()) {
        columns.add(cur.getString(cur.getColumnIndex("name")));
    }
    cur.close();

    return columns;
}

其他回答

public void DeleteColFromTable(String DbName, String TableName, String ColName){
    SQLiteDatabase db = openOrCreateDatabase(""+DbName+"", Context.MODE_PRIVATE, null);
    db.execSQL("CREATE TABLE IF NOT EXISTS "+TableName+"(1x00dff);");
    Cursor c = db.rawQuery("PRAGMA table_info("+TableName+")", null);
    if (c.getCount() == 0) {

    } else {
        String columns1 = "";
        String columns2 = "";
        while (c.moveToNext()) {
            if (c.getString(1).equals(ColName)) {
            } else {
                columns1 = columns1 + ", " + c.getString(1) + " " + c.getString(2);
                columns2 = columns2 + ", " + c.getString(1);
            }
            if (c.isLast()) {
                db.execSQL("CREATE TABLE IF NOT EXISTS DataBackup (" + columns1 + ");");
                db.execSQL("INSERT INTO DataBackup SELECT " + columns2 + " FROM "+TableName+";");
                db.execSQL("DROP TABLE "+TableName+"");
                db.execSQL("ALTER TABLE DataBackup RENAME TO "+TableName+";");
            }
        }
    }
}

只需要调用一个方法

DeleteColFromTable("Database name","Table name","Col name which want to delete");

DB Browser for SQLite允许您添加或删除列。

在主视图中,选择Database Structure,单击表名。一个按钮Modify Table被启用,它会打开一个新窗口,您可以在其中选择列/字段并删除它。

http://www.sqlite.org/lang_altertable.html

正如您在图中看到的,只支持ADD COLUMN。不过,有一个(有点沉重的)变通方法:http://www.sqlite.org/faq.html#q11

作为替代:

如果有一个带模式的表

CREATE TABLE person(
  id INTEGER PRIMARY KEY,
  first_name TEXT,
  last_name TEXT,
  age INTEGER,
  height INTEGER
);

你可以使用CREATE TABLE…AS语句,如CREATE TABLE person2 AS SELECT id, first_name, last_name, age FROM person;,即去掉你不想要的列。然后删除原来的person表并重命名新表。

注意,此方法生成的表没有PRIMARY KEY,也没有约束。为了保留这些表,可以使用其他人描述的方法来创建新表,或者使用临时表作为中间表。

我重写了@Udinic答案,以便代码自动生成表创建查询。它也不需要ConnectionSource。它还必须在事务中完成此操作。

public static String getOneTableDbSchema(SQLiteDatabase db, String tableName) {
    Cursor c = db.rawQuery(
            "SELECT * FROM `sqlite_master` WHERE `type` = 'table' AND `name` = '" + tableName + "'", null);
    String result = null;
    if (c.moveToFirst()) {
        result = c.getString(c.getColumnIndex("sql"));
    }
    c.close();
    return result;
}

public List<String> getTableColumns(SQLiteDatabase db, String tableName) {
    ArrayList<String> columns = new ArrayList<>();
    String cmd = "pragma table_info(" + tableName + ");";
    Cursor cur = db.rawQuery(cmd, null);

    while (cur.moveToNext()) {
        columns.add(cur.getString(cur.getColumnIndex("name")));
    }
    cur.close();

    return columns;
}

private void dropColumn(SQLiteDatabase db, String tableName, String[] columnsToRemove) {
    db.beginTransaction();
    try {
        List<String> columnNamesWithoutRemovedOnes = getTableColumns(db, tableName);
        // Remove the columns we don't want anymore from the table's list of columns
        columnNamesWithoutRemovedOnes.removeAll(Arrays.asList(columnsToRemove));

        String newColumnNamesSeparated = TextUtils.join(" , ", columnNamesWithoutRemovedOnes);
        String sql = getOneTableDbSchema(db, tableName);
        // Extract the SQL query that contains only columns
        String oldColumnsSql = sql.substring(sql.indexOf("(")+1, sql.lastIndexOf(")"));

        db.execSQL("ALTER TABLE " + tableName + " RENAME TO " + tableName + "_old;");
        db.execSQL("CREATE TABLE `" + tableName + "` (" + getSqlWithoutRemovedColumns(oldColumnsSql, columnsToRemove)+ ");");
        db.execSQL("INSERT INTO " + tableName + "(" + newColumnNamesSeparated + ") SELECT " + newColumnNamesSeparated + " FROM " + tableName + "_old;");
        db.execSQL("DROP TABLE " + tableName + "_old;");
        db.setTransactionSuccessful();
    } catch {
        //Error in between database transaction 
    } finally {
        db.endTransaction();
    }


}