When running UPDATE datetime NOW will all rows updated have the same date time

Question

When you run something similar to   UPDATE table SET datetime   NOW      on a table with 1 000 000 000 records and the query takes 10 seconds to run  will all the rows have the exact same time  minutes and seconds  or will they have different times  In other words  will the time be when the query started or when each row is updated   I m running MySQL  but I m thinking this applies to all dbs

User · Accepted Answer

http   dev mysql com doc refman 5 0 en date-and-time-functions html function now      NOW   returns a constant time that indicates the time at which the statement began to execute   Within a stored routine or trigger  NOW   returns the time at which the routine or triggering statement began to execute   This differs from the behavior for SYSDATE    which returns the exact time at which it executes as of MySQL 5 0 13

User · Answer

They should have the same time  the update is supposed to be atomic  meaning that whatever how long it takes to perform  the action is supposed to occurs as if all was done at the same time   If you re experiencing a different behaviour  it s time to change for another DBMS

User · Answer

They should have the same time  the update is supposed to be atomic  meaning that whatever how long it takes to perform  the action is supposed to occurs as if all was done at the same time   If you re experiencing a different behaviour  it s time to change for another DBMS

User · Answer

Assign NOW   to a variable then update the datetime with variable   update date time now     now update like this  UPDATE table SET datetime  update date time    correct the syntax  as per your requirement

User · Answer

They should have the same time  the update is supposed to be atomic  meaning that whatever how long it takes to perform  the action is supposed to occurs as if all was done at the same time   If you re experiencing a different behaviour  it s time to change for another DBMS

User · Answer

The sqlite answer is   update TABLE set mydatetime   datetime  now      in case someone else was looking for it

User · Answer

The sqlite answer is   update TABLE set mydatetime   datetime  now      in case someone else was looking for it

User · Answer

They should have the same time  the update is supposed to be atomic  meaning that whatever how long it takes to perform  the action is supposed to occurs as if all was done at the same time   If you re experiencing a different behaviour  it s time to change for another DBMS

User · Answer

Assign NOW   to a variable then update the datetime with variable   update date time now     now update like this  UPDATE table SET datetime  update date time    correct the syntax  as per your requirement

[mysql] When running UPDATE ... datetime = NOW(); will all rows updated have the same date/time?

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