If you are trying to pull in a table from a SQL server, such as Microsoft SQL Server, and the table contains data in Microsoft SQL Server but appears blank in ArcMap, the table may be using field names that aren't supported by ESRI. You will need to adjust the query.
Here is an example of a query that isn't supported by ESRI:
select ID, Device Name, Date, Meter - Current Day Reading (Last Known Value),
MeterNumber from tableName.dbo.meterReadings
The SQL Server table's column names had spaces, parenthesis, and hyphens, some or all of which are unsupported by ESRI. Thankfully, this only requires a simple fix. To do so, right-click on the table in ArcMap's Table of Contents, go to Properties, go to the Source tab, and change the query to alias the offending field names. You'll need to surround each offending field name with square brackets.
The fixed query looks like this:
select ID, [Device Name] as deviceName, Date, [Meter - Current Day Reading
(Last Known Value)] as currentDayMeterReading, MeterNumber from