let's assume that i have a table with columns such as:
ID SSID BSSID RSSI
1 abcd hs:hd:sd -60
2 abcd hs:hd:po -68
There are about 5000 records with the same SSID, slighltly different BSSID and the LEVEL values. My device is scanning the nearest environment for WiFi networks, therefore I know their MAC address and level of RSSI. I pick 3 with the highest value od RSSI.
First thing I would like to know if it is possible to search through the database to get all the records with the LEVEL value equal or close to 60, for instance 59,58,61.
Secondly, is there a way to query the database to return all the records with the same MAC addresses and RSSI values as from the 3 best scan result? If so, how would that query look like?
EDIT: Thanks for all the answers. What I'm trying to do now is to compare 3 scans with records stored in database with getRequiredData function. I would like to pass 2 parameters to this function, mac address and level and find records with same value for both parameters. The rawQuery seems to be fine, code is compiling but the app is crashing with the first scan. I cant find the cause of it, is it because my logic of getting these parameters is wrong or does it have something to do with query?
public Cursor getRequiredData(String mac, int level){
SQLiteDatabase db = this.getWritableDatabase();
Cursor res = db.rawQuery("SELECT BSSID, RSSI FROM TABLE_NAME WHERE BSSID =? AND RSSI=?", new String[] {mac, level});
return res;
}
scan part:
class WifiReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
sb = new StringBuilder();
Comparator<ScanResult> comparator = new Comparator<ScanResult>() {
#Override
public int compare(ScanResult o1, ScanResult o2) {
return (o1.level>o2.level ? -1 : (o1.level==o2.level ? 0 : 1));
}
};
lista = wifiManager.getScanResults();
Collections.sort(lista, comparator);
for (int i = 0; i < lista.size(); i++) {
scanResult = wifiManager.getScanResults().get(i);
sb.append(new Integer(i + 1).toString() + ". " + (lista.get(i)).SSID + " " + (lista.get(i)).BSSID + " " + (lista.get(i)).level + "\n");
boolean isInserted = myDb.insertData(lista.get(i).SSID.toString(), lista.get(i).BSSID.toString(), lista.get(i).level);
if (isInserted = true)
Toast.makeText(MainActivity.this, "Data inserted", Toast.LENGTH_LONG).show();
else
Toast.makeText(MainActivity.this, "Data not inserted", Toast.LENGTH_LONG).show();
}
for (int i=0; i<4; i++)
{
scanResult = wifiManager.getScanResults().get(i);
match = myDb.getRequiredData(lista.get(i).BSSID.toString(), lista.get(i).level);
}
Log.i("match values: ", DatabaseUtils.dumpCursorToString(match));
txt.setText(sb);
wifiManager.startScan();
}
}
Here is what match contains:
2018-12-10 16:36:26.334 13347-13347/com.example.maciek.wifiscann I/match values:: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor#e1a86d1
0 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
1 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
2 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
3 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
4 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
5 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
<<<<<
To get the 3 rows with the closest values to 60 in column LEVEL:
SELECT * FROM tablename ORDER BY ABS(LEVEL - 60), LEVEL LIMIT 3
For the 2nd part of your question, you should provide sample data of the table. Edit:
From the sample data that you posted I don't see a column RSSI, but if it exists in the table then the SELECT statement is ok.
Change the 2nd parameter of rawQuery() to:
new String[] {mac, String.valueOf(level)}
because level is int.
In onReceive() you use myDb. I don't know how you initialize it.
If the app crashes you must copy the log, the part that identifies the problem and post it.
First thing I would like to know if it is possible to search through
the database to get all the records with the LEVEL value equal or
close to 60, for instance 59,58,61.
SELECT * FROM your_table WHERE level BETWEEN 59 AND 61;
where your_table is the respective table name.
Note if levels are negative (as per example data) then BETWEEN requires the lowest value first so it would be BETWEEN -61 AND -59.
Secondly, is there a way to query the database to return all the
records with the same MAC addresses and RSSI values as from the 3 best
scan result? If so, how would that query look like?
SELECT * FROM your_table WHERE your_mac_address_column = 'the_mac_address_value' AND RSSI = 'the_rssi_value' ORDER BY LEVEL DESC LIMIT 3
Note the above assumes that the MAC address is stored in a column (if NOT then cannot be done unless the mac address can be correlated to a column).
Assumes best LEVEL is lowest so -1 is better than -60 (if not then use ASC instead of DESC)
Again your_table, your_mac_address_column, the_mac_address_value and the_rssi_value would be replaced accordingly with actual values (note that strings should be in single quotes).
I would like to output variables not equal to certain values but it returns an error of
Failed to prepare SQL: SELECT * FROM `tblsuunit` WHERE `unitid` != :qp0
There are two models the first model where am getting the array of ids
public function actionSunits($id){
$unitslocation = new Unitslocation();
$id2 = Unitslocation::find()->where(['officelocationid'=>$id])->all();
foreach( $id2 as $ids){
print_r($ids['unitid']."<br>");
}
}
This outputs the ids as
8
9
11
12
13
14
16
I would then like to take the id and compare another model(units model) and get the id values not similar to the above and output then
So i have added
$idall = Units::find()->where(['!=', 'unitid', $ids])->all();
So the whole controller action becomes
public function actionSunits($id){
$unitslocation = new Unitslocation();
$id2 = Unitslocation::find()->where(['officelocationid'=>$id])->all();
foreach( $id2 as $ids){
$idall = Units::find()->where(['!=', 'unitid', $ids])->all();
}
var_dump($idall);
}
This is the units model table:
If it were working it should return 7 and 10
What could be wrong..
You should fix your code and simply use a not in condition, e.g. :
// $uls will be an array of Unitslocation objects
$uls = Unitslocation::find()->where(['officelocationid'=>$id])->all();
// $uids will contain the unitids
$uids = \yii\helpers\ArrayHelper::getColumn($uls, 'unitid');
// then simply use a not in condition
$units = Units::find()->where(['not in', 'unitid', $uids])->all();
$idall = \yii\helpers\ArrayHelper::getColumn($units, 'unitid');
Read more about ActiveQuery::where() and ArrayHelper::getColumn().
Try with:
$idall = Units::find()->where(['not in','unitid',$ids])->all();
Info: https://github.com/yiisoft/yii2/blob/master/docs/guide/db-query-builder.md
operand 1 should be a column or DB expression. Operand 2 can be either
an array or a Query object.
I want to migrate my iPhone app to a new database version. Since I don't have some version saved, I need to check if certain column names exist.
This Stackoverflow entry suggests doing the select
SELECT sql FROM sqlite_master
WHERE tbl_name = 'table_name' AND type = 'table'
and parse the result.
Is that the common way? Alternatives?
PRAGMA table_info(table_name);
will get you a list of all the column names.
If you do
.headers ON
you will get the desired result.
If you have the sqlite database, use the sqlite3 command line program and these commands:
To list all the tables in the database:
.tables
To show the schema for a given tablename:
.schema tablename
Just for super noobs like me wondering how or what people meant by
PRAGMA table_info('table_name')
You want to use use that as your prepare statement as shown below. Doing so selects a table that looks like this except is populated with values pertaining to your table.
cid name type notnull dflt_value pk
---------- ---------- ---------- ---------- ---------- ----------
0 id integer 99 1
1 name 0 0
Where id and name are the actual names of your columns. So to get that value you need to select column name by using:
//returns the name
sqlite3_column_text(stmt, 1);
//returns the type
sqlite3_column_text(stmt, 2);
Which will return the current row's column's name. To grab them all or find the one you want you need to iterate through all the rows. Simplest way to do so would be in the manner below.
//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
}
}
If you want the output of your queries to include columns names and be correctly aligned as columns, use these commands in sqlite3:
.headers on
.mode column
You will get output like:
sqlite> .headers on
sqlite> .mode column
sqlite> select * from mytable;
id foo bar
---------- ---------- ----------
1 val1 val2
2 val3 val4
An alternative way to get a list of column names not mentioned here that is cross platform and does not rely on the sqlite3.exe shell is to select from the PRAGMA_TABLE_INFO() table value function.
SELECT name FROM PRAGMA_TABLE_INFO('your_table');
name
tbl_name
rootpage
sql
You can check if a certain column exists by querying:
SELECT 1 FROM PRAGMA_TABLE_INFO('your_table') WHERE name='column1';
1
This is what you use if you don't want to parse the result of select sql from sqlite_master or pragma table_info.
Note this feature is experimental and was added in SQLite version 3.16.0 (2017-01-02).
Reference:
https://www.sqlite.org/pragma.html#pragfunc
To get a list of columns you can simply use:
.schema tablename
I know it is an old thread, but recently I needed the same and found a neat way:
SELECT c.name FROM pragma_table_info('your_table_name') c;
When you run the sqlite3 cli, typing in:
sqlite3 -header
will also give the desired result
.schema table_name
This will list down the column names of the table from the database.
Hope this will help!!!
you can use Like statement if you are searching for any particular column
ex:
SELECT * FROM sqlite_master where sql like('%LAST%')
This command below sets column names:
.header on
Then, this is how it looks like below:
sqlite> select * from user;
id|first_name|last_name|age
1|Steve|Jobs|56
2|Bill|Gates|66
3|Mark|Zuckerberg|38
And this command below unsets column names:
.header off
Then, this is how it looks like below:
sqlite> select * from user;
1|Steve|Jobs|56
2|Bill|Gates|66
3|Mark|Zuckerberg|38
And these commands show the details of the command ".header":
.help .header
Or:
.help header
Then, this is how it looks like below:
sqlite> .help .header
.headers on|off Turn display of headers on or off
In addition, this command below sets the output mode "box":
.mode box
Then, this is how it looks like below:
sqlite> select * from user;
┌────┬────────────┬────────────┬─────┐
│ id │ first_name │ last_name │ age │
├────┼────────────┼────────────┼─────┤
│ 1 │ Steve │ Jobs │ 56 │
│ 2 │ Bill │ Gates │ 66 │
│ 3 │ Mark │ Zuckerberg │ 38 │
└────┴────────────┴────────────┴─────┘
And, this command below sets the output mode "table":
.mode table
Then, this is how it looks like below:
sqlite> select * from user;
+----+------------+------------+-----+
| id | first_name | last_name | age |
+----+------------+------------+-----+
| 1 | Steve | Jobs | 56 |
| 2 | Bill | Gates | 66 |
| 3 | Mark | Zuckerberg | 38 |
+----+------------+------------+-----+
And these commands show the details of the command ".mode":
.help .mode
Or:
.help mode
Then, this is how it looks like below:
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
In order to get the column information you can use the following snippet:
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);
}
//JUST little bit modified the answer of giuseppe which returns array of table columns
+(NSMutableArray*)tableInfo:(NSString *)table{
sqlite3_stmt *sqlStatement;
NSMutableArray *result = [NSMutableArray array];
const char *sql = [[NSString stringWithFormat:#"PRAGMA table_info('%#')",table] UTF8String];
if(sqlite3_prepare(md.database, sql, -1, &sqlStatement, NULL) != SQLITE_OK)
{
NSLog(#"Problem with prepare statement tableInfo %#",
[NSString stringWithUTF8String:(const char *)sqlite3_errmsg(md.database)]);
}
while (sqlite3_step(sqlStatement)==SQLITE_ROW)
{
[result addObject:
[NSString stringWithUTF8String:(char*)sqlite3_column_text(sqlStatement, 1)]];
}
return result;
}
.schema
in sqlite console when you have you're inside the table
it looks something like this for me ...
sqlite>.schema
CREATE TABLE players(
id integer primary key,
Name varchar(255),
Number INT,
Team varchar(255)
This is an old question, but here is an alternative answer that retrieves all the columns in the SQLite database, with the name of the associated table for each column :
WITH tables AS (SELECT name tableName, sql
FROM sqlite_master WHERE type = 'table' AND tableName NOT LIKE 'sqlite_%')
SELECT fields.name, fields.type, tableName
FROM tables CROSS JOIN pragma_table_info(tables.tableName) fields
This returns this type of result:
{
"name": "id",
"type": "integer",
"tableName": "examples"
}, {
"name": "content",
"type": "text",
"tableName": "examples"
}
For a simple table containing an identifier and a string content.
function getDetails(){
var data = [];
dBase.executeSql("PRAGMA table_info('table_name') ", [], function(rsp){
if(rsp.rows.length > 0){
for(var i=0; i<rsp.rows.length; i++){
var o = {
name: rsp.rows.item(i).name,
type: rsp.rows.item(i).type
}
data.push(o);
}
}
alert(rsp.rows.item(0).name);
},function(error){
alert(JSON.stringify(error));
});
}
-(NSMutableDictionary*)tableInfo:(NSString *)table
{
sqlite3_stmt *sqlStatement;
NSMutableDictionary *result = [[NSMutableDictionary alloc] init];
const char *sql = [[NSString stringWithFormat:#"pragma table_info('%s')",[table UTF8String]] UTF8String];
if(sqlite3_prepare(db, sql, -1, &sqlStatement, NULL) != SQLITE_OK)
{
NSLog(#"Problem with prepare statement tableInfo %#",[NSString stringWithUTF8String:(const char *)sqlite3_errmsg(db)]);
}
while (sqlite3_step(sqlStatement)==SQLITE_ROW)
{
[result setObject:#"" forKey:[NSString stringWithUTF8String:(char*)sqlite3_column_text(sqlStatement, 1)]];
}
return result;
}
I know it's too late but this will help other.
To find the column name of the table, you should execute select * from tbl_name and you will get the result in sqlite3_stmt *. and check the column iterate over the total fetched column. Please refer following code for the same.
// sqlite3_stmt *statement ;
int totalColumn = sqlite3_column_count(statement);
for (int iterator = 0; iterator<totalColumn; iterator++) {
NSLog(#"%s", sqlite3_column_name(statement, iterator));
}
This will print all the column names of the result set.
I was able to retrieve table names with corresponding columns by using one sql query, but columns output is comma separated. I hope it helps somebody
SELECT tbl_name, (SELECT GROUP_CONCAT(name, ',') FROM PRAGMA_TABLE_INFO(tbl_name)) as columns FROM sqlite_schema WHERE type = 'table';
Get a list of tables and columns as a view:
CREATE VIEW Table_Columns AS
SELECT m.tbl_name AS TableView_Name, m.type AS TableView, cid+1 AS Column, p.*
FROM sqlite_master m, Pragma_Table_Info(m.tbl_name) p
WHERE m.type IN ('table', 'view') AND
( m.tbl_name = 'mypeople' OR m.tbl_name LIKE 'US_%') -- filter tables
ORDER BY m.tbl_name;
//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 )
}
If you're using the SQLite3, INFORMATION_SCHEMA is not supported. Use PRAGMA table_info instead. This will return 6 rows of information about the table. To fetch the column name (row2), use a for loop like the following
cur.execute("PRAGMA table_info(table_name)") # fetches the 6 rows of data
records = cur.fetchall()
print(records)
for row in records:
print("Columns: ", row[1])
For use in Python with sqlite3
Top answer PRAGMA table_info() returns a list of tuples, which might not be suitable for further processing, e.g.:
[(0, 'id', 'INTEGER', 0, None, 0),
(1, 'name', 'TEXT', 0, None, 0),
(2, 'age', 'INTEGER', 0, None, 0),
(3, 'profession', 'TEXT', 0, None, 0)]
When using sqlite3 in Python, simply add a list comprehension in the end to filter out unwanted information.
import sqlite3 as sq
def col_names(t_name):
with sq.connect('file:{}.sqlite?mode=ro'.format(t_name),uri=True) as conn:
cursor = conn.cursor()
cursor.execute("PRAGMA table_info({}) ".format(t_name))
data = cursor.fetchall()
return [i[1] for i in data]
col_names("your_table_name")
Result
["id","name","age","profession"]
DISCLAIMER: Do not use in production as this snippet is subject to possible SQL injection!