How to convert CHAR values into DATETIME values in SQL Server


The following information discusses how to convert CHAR values into DATETIME values so that a SMALLINT value can be subtracted and a START_TIME value can be obtained.

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To begin with, the character date and time must be converted into the SQL Server datetime format. Then the SMALLINT value can be subtracted to obtain START_TIME. Both tasks can be performed in a single SQL expression; however, it is easier to understand the process if both tasks are considered separately.

For example, if the time value is stored in a column named "term_time" with a format of HHMMSS, and the date value is stored in a column named "term_date" with a format of YYMMDD, these values can be converted to the SQL Server datetime with the following call:

   convert(datetime,term_date+" "+
substring(term_time,5,2) )

Given a date in SQL Server datetime format, it is easy to add or subtract a given amount of seconds, minutes, days, and so forth. For example, assuming the SMALLINT value ("@delta") is in seconds, the following function will return the start date/time:


The entire expression can be put into the following select statement so it is executed for each row in the input table. "@delta" is assumed to be an input parameter. If "@delta" is in units other than seconds, the first parameter of dateadd must be changed to reflect the correct units (minutes, days, and so forth).

   select  dateadd( ss, -(@delta), convert(datetime,term_date+" "+
substring(term_time,5,2) ))
from t1

ID do Artigo: 69133 - Última Revisão: 10 de jul de 2008 - Revisão: 1