In my database there are 3 column which is Name, Age, Gender.
In the program, I only want to use 1 search button. When the button is clicked, the program determine which 3 of the textbox has input and search for the right data.
How do you work with the query? For example if Name and Gender has text, the query :
"Select * from table Where (Name = #name) AND (Gender = #gender)"
And when only name is entered, I only query for the name. Must I check textbox by textbox whether there is user input and then write multiple query for each of them? Or is there a better way to do this?
Edit (29/5/16) : I tried doing this another way like this
myCommand = New MySqlCommand("Select * from project_record Where
(FloatNo = #floatNo OR FloatNo = 'None') AND
(DevCompanyName = #devCompanyName OR DevCompanyName = 'None') AND
(DevType = #devType OR DevType = 'None') AND
(LotPt = #lotPt OR LotPt = 'None') AND
(Mukim = #mukim OR Mukim = 'None') AND
(Daerah = #daerah OR Daerah = 'None') AND
(Negeri = #negeri OR Negeri = 'None') AND
(TempReference = #tempRef OR TempReference = 'None')", sqlConn)
But as you can guess already it will not work efficiently as well because if I only enter input for DevType and leave other textboxes blank, the query will not pull up all the records for DevType only. It will just display as no records.
Select * from table
Where (Name = #name OR #name is Null)
AND (Gender = #gender OR #gender is Null)
...
it should be one query
Other answers have explained how to simplify the query. It is especially important to get rid of the ORs, since they inhibit any use of indexes.
Once you have the query build cleanly, you need to think about the dataset and decide which columns are usually used for filtering. Then make a few INDEXes for them. You won't be able to provide 'all' possible indexes, hence my admonition that you think about the dataset.
When building indexes, you can have single-column or multiple-column indexes. For your type of data, I would suggest starting with several 2-column indexes. Make sure each index starts with a different column.
For Where (Name = #name) AND (Gender = #gender), here are some notes:
INDEX(gender) is useless because of low 'cardinality';
INDEX(gender, name) might be useful, but the following would be better:
INDEX(name)
Things like name and DevCompanyName are virtually unique, so a 1-column index is probably good.
If you had gender and age, then INDEX(age, gender) might be useful.
MySQL will almost never use two indexes for a single SELECT.
By the way, the construction of the WHERE could be done in a Stored Procedure. You would need CONCAT, PREPARE, etc.
Original answer
(scroll down to see update)
Can you try the following:
build a list only including values of the textboxes that have an input
set a string of the join the items of that list together with the " AND " string
append that string to your standard SELECT statement
The code looks like this:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim Predicate1 As String = Me.TextBox1.Text
Dim Predicate2 As String = Me.TextBox2.Text
Dim Predicate3 As String = Me.TextBox3.Text
Dim PredicateList As New List(Of String)
Dim WhereClause As String
Dim Query As String
If Predicate1 <> String.Empty Then
PredicateList.Add("Name=""" & Predicate1 & """")
End If
If Predicate2 <> String.Empty Then
PredicateList.Add("Age=""" & Predicate2 & """")
End If
If Predicate3 <> String.Empty Then
PredicateList.Add("Gender=""" & Predicate3 & """")
End If
WhereClause = String.Join(" AND ", PredicateList.ToArray)
Query = "SELECT * FROM TABLE WHERE " & WhereClause
MessageBox.Show(Query)
End Sub
Update
Further to the comments re SQL injection, here is an updated sample.
Dim Command As SqlClient.SqlCommand
Dim Predicate1 As String = Me.TextBox1.Text
Dim Predicate2 As String = Me.TextBox2.Text
Dim Predicate3 As String = Me.TextBox2.Text
Dim ParameterList As New List(Of SqlClient.SqlParameter)
Dim PredicateList As New List(Of String)
Dim BaseQuery As String = "SELECT * FROM TABLE WHERE "
If Predicate1 <> String.Empty Then
PredicateList.Add("name = #name")
ParameterList.Add(New SqlClient.SqlParameter("#name", Predicate1))
End If
If Predicate2 <> String.Empty Then
PredicateList.Add("age = #age")
ParameterList.Add(New SqlClient.SqlParameter("#age", Predicate2))
End If
If Predicate3 <> String.Empty Then
PredicateList.Add("gender = #gender")
ParameterList.Add(New SqlClient.SqlParameter("#gender", Predicate3))
End If
Command = New SqlClient.SqlCommand(BaseQuery & String.Join(" AND ", PredicateList.ToArray))
Command.Parameters.AddRange(ParameterList.ToArray)
COALESCE is your friend here. You can use it to make the where clause ignore comparisons where the parameter is NULL.
Select * from table Where (Name = COALESCE(#name,table.Name))
AND (Gender = COALESCE(#gender,table.Gender))
So, if the #name parameter is NULL, COALESCE(#name,table.Name) will return the value of the 'Name' column of the current row and (Name = COALESCE(#name,table.Name)) will always be true.
This assumes that if no value is entered in a textbox the corresponding parameter will be NULL. If instead it is a value such as 'None', you can use the NULLIF function to map 'None' to NULL
Select * from table Where
(Name = COALESCE( NULLIF( #name, 'None'), table.Name))
AND (Gender = COALESCE( NULLIF( #gender, 'None'), table.Gender))
How to implement a more efficient search?
The answer partly depends on what your definition of efficient is. I suspect you mean less code and fewer if blocks etc. But fundamentally, running a new SELECT * query to apply a filter is inefficient because your base data set can be all the rows and you just fiddle with the users View of it.
I have a DB with random data in columns for Fish, Color (string), Bird, Group (int) and Active which should be similar enough for Name, Age and Gender in the question - or that other long thing at the bottom.
DataTable
Fill a datatable and bind it to a DGV:
' form level object
Private dtSample As DataTable
...
' elsewhere
Dim sql = "SELECT Id, Name, Descr, `Group`, Fish, Bird, Color, Active FROM Sample"
Using dbcon As MySqlConnection = New MySqlConnection(MySQLConnStr)
' create SELECT command with the Query and conn
Dim cmd As New MySqlCommand(sql, dbcon)
...
daSample.Fill(dtSample)
daSample.FillSchema(dtSimple, SchemaType.Source)
End Using
dgv2.DataSource = dtSample
Going forward, we can filter the user's view of that table without issuing a new query.
Filter Controls
If some of the fields are limited to certain selections, for instance Gender, you can use a ComboBox instead of a TextBox. This is to help the user succeed and avoid typos (Make or Mael instead of Male; or here, correctly spelling Baracuda I mean Baraccuda, er Barracuda correctly.
For illustration purposes, Fish is something where the user can type in anything at all, but Bird is constrained to a set of choices. If there is a Bird table, cboBird can be bound or populated from it. But you may also be able to populate it from the master/base table:
Dim birds = dtSample.AsEnumerable.Where(Function(d) d.IsNull(5) = False).
Select(Function(d) d.Field(Of String)("Bird")).
Distinct.
ToArray()
cboBird.Items.AddRange(birds)
If "Finch" is a legal choice but there are none in the database, it wont show in the list. Depending on the app, this can be a Good Thing:
If the user filters on Finch and there a no resulting records, you won't need a MessageBox or StatusBar message explaining the empty result set.
If something is not in the list, you are signalling up front that there are none of those. It then becomes a matter of training why a known element isnt in the list.
On the other hand, you'd have to repopulate those filter controls each time before they are used in case new records were added recently. If the controls are on a Dialog or different TabPage, this is easy to do as needed.
It isnt always applicable, but it can help the user avoid typos.
It depends on the app whether either method is of value.
DBNull / 'none'
I am not sure why you are adding 'none' to each clause. If someone want to see all the 'John` or all the 'Cod' records, it doesn't seem like they would also be interested in 'none'. Personally, Null/DBNull seems a better way to handle this, but it is easy to add or not add either form.
It would seem more valuable to filter to just those with DBNull/None. The code above for the Bird List filters out DBNull and I would do so for none as well. Then, before the result is added to the ComboBox, add a `None' item first so it is at the top.
Again it depends on what the app does; Or = 'None', may make perfect sense in this case.
Filter
Using a TextBox for Fish and Group, a ComboBox for Bird and Color and a CheckBox for Active, the code can form the filter thusly:
Dim filterTerms As New List(Of String)
Dim filterFmt = "{0} = '{1}' "
' OR:
' Dim filterFmt = "{0} = '{1}' OR {0} Is Null"
' OR:
' Dim filterFmt = "{0} = '{1}' OR {0} = 'none'"
If String.IsNullOrEmpty(tbSearchFish.Text) = False Then
Dim txt = tbSearchFish.Text.Replace("'", "''")
filterTerms.Add(String.Format(filterFmt, "Fish", txt))
End If
If cboBird.SelectedIndex > -1 Then
filterTerms.Add(String.Format(filterFmt, "Bird", cboBird.SelectedItem.ToString))
End If
If String.IsNullOrEmpty(tbGroup.Text) = False Then
Dim n As Int32
If Int32.TryParse(tbGroup.Text, n) Then
filterTerms.Add(String.Format(filterFmt, "[Group]", n))
End If
End If
If cboColor.SelectedIndex > -1 Then
filterTerms.Add(String.Format(filterFmt, "Color", cboColor.SelectedItem.ToString))
End If
If chkActive.Checked Then
' NOTE: I do not have TreatTinyAsBoolean turned on
' for some reason
filterTerms.Add(String.Format(filterFmt, "Active", "1"))
End If
If filterTerms.Count > 0 Then
Dim filter = String.Join(" AND ", filterTerms)
dtSample.DefaultView.RowFilter = filter
Dim rows = dtSample.DefaultView.Count
End If
Use whichever filterFmt is appropriate for what the app needs to do
A filter term is only added to the list if the related control has a value (as per above, this could include a 'None').
For the TextBox, it escapes any embedded ticks such as might be found in names like O'Malley or D'Artgnan. It replaces one tick with two.
Since Group is a numeric, a valid Int32 input is tested
If there are elements in the filterTerms list, a filter string is created
The filter is applied to the DefaultView.Filter (you can use also use a DataView or a BindingSource) so that the code need not query the database to provide filter capabilities.
Rows will tell you how many rows are in the current View.
The only halfway tricky one is a Boolean like Gender or Active because those actually resolve to three choices: {Any/Either, A, B}. For that, I would use a ComboBox and ignore it for SelectedIndex 0 as well. I didn't bother with this because the Combo concept is amply covered. Result:
Is it More "Efficient"?
It still depends.
It doesn't re-query the database to get rows the app can already have.
No new DBConnection, DBCommand or other DBProvider objects are created, just a list.
No need to dynamically create a SQL statement with N parameters in a loop to avoid SQL injection/special words and chars.
It doesn't even query the database for the items for the filter terms. If there is a static list of them in the DB, they could be loaded once, the first time they use the filters.
It is easy to remove the filter, no need to query yet again without WHERE clauses.
A ComboBox where applicable helps the user find what they want and avoid typos.
Is the SQL "cleaner". more "efficient? The code doesn't really mess with new SQL, just some WHERE clauses.
Is there less code? I have no idea since we just see the result. It doesnt string me as a lot of code to do what it does.
In my database there are 3 column which is Name, Age, Gender. In the program, I only want to use 1 search button. When the button is clicked, the program determine which 3 of the textbox has input and search for the right data.
And when only name is entered, I only query for the name. Must I check textbox by textbox whether there is user input and then write multiple query for each of them? Or is there a better way to do this?
SELECT * FROM `table`
WHERE (`name` = #name AND `name` IS NOT NULL)
OR (`age` = #age AND (`age`>0 OR `age` IS NOT NULL))
OR (`gender` = #gender AND `gender` IS NOT NULL);
With the above query if all text boxes have value, the result will not be one record (as if you where using logical AND between fields). If you want only that record you will filter it server-side with php from the rest of the results.
You can check the results on your own in this Fiddle
EDIT
In order to solve the above inconvenience (not bringing easily single results when needed) i got a little help from this answer and re-wrote the above query as:
SELECT *, IF(`name`=#name, 10, 0) + IF(`age`=#age, 10, 0) + IF(`gender`=#gender, 10, 0) AS `weight`
FROM `table`
WHERE (`name` = #name AND `name` IS NOT NULL)
OR (`age` = #age AND (`age`>0 OR `age` IS NOT NULL))
OR (`gender` = #gender AND `gender` IS NOT NULL)
HAVING `weight`=30;
OR to still get all records with a weight on result
SELECT *, IF(`name`=#name, 10, 0) + IF(`age`=#age, 10, 0) + IF(`gender`=#gender, 10, 0) AS `weight`
FROM `table` WHERE (`name` = #name AND `name` IS NOT NULL)
OR (`age` = #age AND (`age`>0 OR `age` IS NOT NULL))
OR (`gender` = #gender AND `gender` IS NOT NULL)
ORDER BY `weight` DESC;
You were pretty close. Let's look at
(FloatNo = #floatNo OR FloatNo = 'None')
So you want the field either to be the given input or 'None'? But there are (supposedly) no records in your table with FloatNo 'None'. What you really want to do is find out whether the input is none (i.e. empty):
(FloatNo = #floatNo OR #floatNo = '')
And for the case the user types in a blank by mistake, you can ignore this, too:
(FloatNo = #floatNo OR TRIM(#floatNo) = '')
The whole thing:
myCommand = New MySqlCommand(
"Select * from project_record Where
(FloatNo = #floatNo OR TRIM(#floatNo) = '') AND
(DevCompanyName = #devCompanyName OR TRIM(#devCompanyName) = '') AND
(DevType = #devType OR TRIM(#devType) = '') AND
(LotPt = #lotPt OR TRIM(#lotPt) = '') AND
(Mukim = #mukim OR TRIM(#mukim) = '') AND
(Daerah = #daerah OR TRIM(#daerah) = '') AND
(Negeri = #negeri OR TRIM(#negeri) = '') AND
(TempReference = #tempRef OR TRIM(#tempRef) = '')", sqlConn)
What is wrong with your approach?
Just change
(FloatNo = #floatNo OR FloatNo = 'None')
to
(FloatNo = #floatNo OR FloatNo = '' or FloatNo IS NULL)
And do that for every criteria.
Your query will respect empty values and NULL values after that.
Hello Everyone Good Afternoon,
I have 5 Fields in MySQL and there are:
ItemCode
Description
OrderQty
ApprovedQty
UoM
UnitPrice
Total
I cant explain it using proper words but I hope you will understand it by letting me show to you the table.
_______________________________________________________________
|ItemCode|Description|OrderQty|ApprovedQty|UOM|UnitPrice|Total|
---------------------------------------------------------------
|12345678|Ketchup |12.00 |0.00 |PC |1.00 |12.00|
|67891111|Soy Sauce |0.00 |12.00 |PC |1.00 |12.00|
---------------------------------------------------------------
Now you see it, I hope you can understand it now.
Here is my Question, I have a Code that will transfer the Data above into a Datagridview but theres a twist and that twist is the Question.
Here it is:
How can I Display the Data like this; If ApprovedQty is 0.00 then the Data in the OrderQty will display but if ApprovedQty is not 0.00 regardless of what data is in the OrderQty the ApprovedQty will be Show.
Something like this.
Based on the Table above
___________________________________________________
|ItemCode|Description|OrderQty|UOM|UnitPrice|Total|
---------------------------------------------------
|12345678|Ketchup |12.00 |PC |1.00 |12.00|
|67891111|Soy Sauce |12.00 |PC |1.00 |12.00|
---------------------------------------------------
Here is my code but it only shows the Approved Qty
Private Sub loadfinalpurch1()
Dim con1 As MySqlConnection = New MySqlConnection("server=localhost;userid=root;password=admin1950;database=inventory")
Dim sql1 As MySqlCommand = New MySqlCommand("Select ItemCode,Description,ApprovedQty,UoM,UnitPrice,Total from final_purch where PRnumber = '" & Label2.Text & "' and Added is NULL OR Added ='';", con1)
Dim ds1 As DataSet = New DataSet
Dim adapter1 As MySqlDataAdapter = New MySqlDataAdapter
con1.Open()
adapter1.SelectCommand = sql1
adapter1.Fill(ds1, "MyTable")
DataGridView1.DataSource = ds1.Tables(0)
con1.Close()
With DataGridView1
.RowHeadersVisible = False
.Columns(0).HeaderCell.Value = "Item Code"
.Columns(1).HeaderCell.Value = "Description"
.Columns(2).HeaderCell.Value = "Order Qty"
.Columns(3).HeaderCell.Value = "UOM"
.Columns(4).HeaderCell.Value = "Unit Price"
.Columns(5).HeaderCell.Value = "Total Amount"
End With
DataGridView1.Columns.Item(0).Width = 90
DataGridView1.Columns.Item(1).Width = 200
DataGridView1.Columns.Item(2).Width = 90
DataGridView1.Columns.Item(3).Width = 90
DataGridView1.Columns.Item(4).Width = 100
DataGridView1.Columns.Item(5).Width = 100
DataGridView1.ColumnHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.BottomCenter
Dim checkBoxColumn As New DataGridViewCheckBoxColumn()
checkBoxColumn.HeaderText = "Tag"
checkBoxColumn.Width = 30
checkBoxColumn.Name = "checkBoxColumn"
DataGridView1.Columns.Insert(0, checkBoxColumn)
End Sub
I hope you get my point.Do I have something to do with the MYSQL Command? with My Code? I don`t know how to achieve this.
TYSM For Future Help
You don't do that condition anywhere, you could do it on your code or directly changing your query:
Select ItemCode,
Description,
IF(ApprovedQty = 0, OrderQty, ApprovedQty) as myApprovedQty,
UoM,
UnitPrice,
Total from final_purch where PRnumber = '" & Label2.Text & "' and Added is NULL OR Added ='';", con1
You should implement this in your SQL using a case statement.
https://dev.mysql.com/doc/refman/5.7/en/case.html
The above answers using the IF() function are correct, but in my opinion it is better to use the CASE-WHEN so as to match other database engines like Microsoft SQL Server and Oracle.
SELECT
ItemCode,
Description,
IF (ApprovedQty = 0, OrderQty, ApprovedQty),
UoM,
UnitPrice,
Total
FROM table
I have a table in access with two fields: state and city. The state is unique and the city should be the same.
I have a table that shows duplicate states with the same city. I want to make the city that is duplicate to be random within the state. I have another table that calls out the cities in the states.
I currently have:
State
Washington Seattle
Washington Seattle
I want it to be:
Washington Seattle
Washington Bellevue
How do i remove the duplicate city and replace one of it with a random city in the state like the example above?
Assuming that i have a separate table that I can create to call out all the cities in a state.
I have no idea how to tackle this issue. Thanks for the help.
One possible way to do this (based on your comment) is to add two fields to your city table. Call it something like [Used] and [DateUsed]. use some type of random function to pick your cities. As you use the city, change the [used] field to true and put today's date in the [Dateused] field. Use a query to pull only the cities that are marked False. You can run a daily query, any [Dateused] that is older than 2 days you can clear the true flag from the [used] field and clear the [DateUsed] field.
dim db as dao.databse
dim rs as dao.recordset
dim sql as string
dim x as integer
x = 0
set db = currentdb
Do While X < 20
sql = "SELECT * FROM [tblcities] WHERE [Used] = false AND stateID = " & some value for stateID
set rs = db.openrecordset(SQL,dbopenDynaset)
if rs.recordcount > 0
rs.movefirst
do while not rs.eof
if randomfunction() = true //just an example, you'll have to come up with the random function on your own.
SQL = "UPDATE [tblCities] SET [Used] = True, [DateUsed] = DATE() WHERE StateID = " & Some Value for StateID & " AND CityName = '" & rs!cityName & "'"
docmd.RunQuery SQL
break do
end if
rs.movenext
loop
end if
set rs = nothing
x = x + 1
loop
set rs = nothing
set db = nothing
(rough code, I'm sure there are lost of little typo or syntax error, but this not meant to be a complete example, only to point you in a direction.)
I am sure this is fairly simple put I am having trouble getting started on this. I use a Form to invoice clients which includes the field [Billing_Month]. What I'm looking to accomplish is this. When I create a new invoice, the [Billing_Month] will look to the last invoice created (use [Invoice_#] with DMax?), and populate the value from that that invoices [Billing_Month]
I have thought to use: Billing_Month = DMax ("Billing_Month", "frmInvoices"), but this doesn't specifically get me the last invoice, it would just look for the highest Billing_Month, which is a text field.
I have thought to use: Billing_Month = DLookup ("Billing_Month", "frmInvoices"), But this doesn't get me the last invoice to pull from.
I'd use a custom function for this - assuming the underlying table is called tblInvoices:
Function GetBillingMonthOfLatestInvoice()
Const SQL = "SELECT TOP 1 Billing_Month FROM tblInvoices ORDER BY [Invoice_#] DESC"
Dim RS AS DAO.Recordset
Set RS = CurrentDb.OpenRecordset(SQL)
If RS.EOF Then
GetBillingMonthOfLatestInvoice = Null
Else
GetBillingMonthOfLatestInvoice = RS(0)
End If
End Function
Update
The above code can be generalised to return other related fields like so:
Function GetValueForLatestInvoice(FieldToLookUp As String)
Dim RS As DAO.Recordset, SQL As String
SQL = "SELECT TOP 1 " + FieldToLookUp + " FROM tblInvoices ORDER BY [Invoice_#] DESC"
Set RS = CurrentDb.OpenRecordset(SQL)
If RS.EOF Then
GetValueForLatestInvoice = Null
Else
GetValueForLatestInvoice = RS(0)
End If
End Function
To use, copy the code to a new standard module, then for each relevant text box on the form, set its Default Value property in the Properties window to something like this:
=GetValueForLatestInvoice("Billing_Month")
That would be for the text box holding the billing month value; for the one holding the billing year, you would use
=GetValueForLatestInvoice("Billing_Year")
You can use a combination of both DLookup() and DMax() like so:
DLookup("Billing_Month","tblInvoices","[Invoice_#]=" & DMax("[Invoice_#]","tblInvoices"))
In VB 2010 I'm trying to show the DisplayMember in ProperCase without modifying my existing MySQL tables.
A snippet of my code looks like this:
Dim sql0 As String = "SELECT business, customer_id FROM customers WHERE cab = '1'"
Dim data0 As New MySqlDataAdapter(sql0, main.conn)
Dim ds0 As New DataSet
ds0.Clear()
data0.Fill(ds0, "customers")
cmb_company.DataSource = ds0
cmb_company.DisplayMember = "customers.business"
cmb_company.ValueMember = "customers.customer_id"
Ive tried something like this:
cmb_company.DisplayMember = StrConv("customers.business_name", VbStrConv.ProperCase)
but this only changes the case of the part in quotes, and not the actual returned values. I also tried querying from MySQL like this:
"SELECT UPPER(business), customer_id FROM customers WHERE cab = '1'"
but this fails to return the "business" field..
I'd love it if my combobox had proper case without changing everything.
I appreciate any suggestions!
Use the second one, but use an alias like this:
"SELECT UPPER(business) AS Business, customer_id FROM customers WHERE cab = '1'"
MySQL documentation:
A select_expr can be given an alias using AS alias_name. The alias is
used as the expression's column name and can be used in GROUP BY,
ORDER BY, or HAVING clauses. For example:
SELECT CONCAT(last_name,', ',first_name) AS full_name FROM mytable
ORDER BY full_name;
It seems a bit silly to use a while loop to achieve this especially after filling the table with an adapter. I suppose I could have just skipped the .fill and added the items manually through the loop, all while ProperCasing them. Anyway, here is my code:
Dim sql1 As String = "SELECT * FROM table"
Dim data1 As New MySqlDataAdapter(sql1, main.conn)
Dim ds1 As New DataSet
ds1.Clear()
data1.Fill(ds1, "table")
cmb_buyout.DataSource = ds1
Dim i As Integer = 0
While i < ds1.Tables(0).Rows.Count
Dim name As String = StrConv(ds1.Tables(0).Rows(i).Item(1).ToString, VbStrConv.ProperCase)
ds1.Tables(0).Rows(i).Item(1) = name
i += 1
End While
cmb_buyout.DisplayMember = "table.buyoutType"
cmb_buyout.ValueMember = "table.id"
To anyone trying to accomplish this, it is probably simpler to just change the case on the entries in the DB. I might just end up doing this!