I am trying to replace a foreach
statement with a single SQL query, my code I want to change looks like this:
this.Settings = new List<Setting>()
{
// Write all the settings from the VB
new Setting() { Name = "NOOFORDERS", Value = null },
new Setting() { Name = "ORDNVGREQ", Value = null },
new Setting() { Name = "IncWendsDel", Value = null },
new Setting() { Name = "AUTOEMAIL_INVOICE", Value = null },
new Setting() { Name = "REQEMAIL_INVOICE", Value = null },
new Setting() { Name = "REQEMAIL_SALES", Value = null },
new Setting() { Name = "REQEMAIL_PICKSLIP", Value = null },
new Setting() { Name = "REQEMAIL_DESPATCH", Value = null },
new Setting() { Name = "CARRPARTSHIP", Value = null },
new Setting() { Name = "DELNOTEREQ", Value = null },
new Setting() { Name = "REQ_CARRPARTSHIP", Value = null },
new Setting() { Name = "BUDGETREQ", Value = null },
new Setting() { Name = "PriceList", Value = null },
new Setting() { Name = "EmployeeRenew", Value = null },
new Setting() { Name = "Warehouse", Value = null },
new Setting() { Name = "EmployeeDetails", Value = null },
};
var value = this.db.tblbus_setvalues.Where( x => x.SettingID == setting.Name && x.BusinessCode == this.Business.BusinessCode ).FirstOrDefault().Value;
switch (value.GetType())
{
case typeof(bool):
(value) ? setting.Value = "true" : setting.Value = "false";
break;
default:
setting.Value = value.ToString();
break;
}
if ( !string.IsNullOrEmpty(setting.Value) ) setting.Value = this.db.tblbus_settings.Where( x => x.SettingID == setting.Name ).FirstOrDefault().Default.ToString();
My SQL which I want to replace the above code with looks like this:
SELECT t1.SettingID, t2.Value, t1.Default
FROM `tblbus_settings` t1
LEFT JOIN `tblbus_setvalues` t2
ON t1.SettingID = t2.SettingID
WHERE `BusinessCode` = "XXX" // Dependency
AND t1.`BusType` = "CUS"
Can anyone help me write an IF statement onto this SQL query which will only display the t2.Value
if the t1.Default
is null ?
I tried things like:
IF(t2.value == NULL) { t1.Default }
ELSE { t2.Value }
But they all give me SQL syntax errors.
您可以使用合并函数,该函数返回列表中的第一个非NULL值,如果没有非NULL值,则返回NULL:
SELECT t1.SettingID, COALESCE(t2.Value, t1.Default) FROM ...
Something like this?
SELECT t1.SettingID, t2.Value, t1.Default,
CASE t1.Default IS NOT NULL
THEN t1.Default
ELSE t2.Value
FROM `tblbus_settings` t1
LEFT JOIN `tblbus_setvalues` t2
ON t1.SettingID = t2.SettingID
WHERE `BusinessCode` = "XXX" // Dependency
AND t1.`BusType` = "CUS"
See this for meore https://msdn.microsoft.com/en-gb/library/ms181765.aspx
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