Would one of a couple going to a bar for a moderate amount of alcoholic drink before a nuptial Mass have any effect on the validity of a marriage?
Marriage is a serious thing. Matrimony should be entered into seriously and soberly.
For most people, the decision to marry is the most important decision of their lives.
Matrimonial consent must be freely given by persons capable of positing such a momentous juridic act.
Christian marriage is a sacred, indeed usually sacramental, act. By its very nature it requires clarity of mind and purity of intention.
Why someone would want to take such a serious step with senses dulled by intoxicants is beyond me.
However, for consent to be invalid, a person would need to be so intoxicated that she was truly incapable of using reason in a manner proportionate to marriage. Someone who was merely tipsy, however stupid that would be, would not be unable to marry.
Apart from why someone would get drunk before her wedding, why would someone want to marry someone who would get drunk before her wedding?