1.0Simple Talkhttps://www.red-gate.com/simple-talkJoe Celkohttps://www.red-gate.com/simple-talk/author/joe-celko/rich600338<blockquote class="wp-embedded-content" data-secret="Ynk21Cku8a"><a href="https://www.red-gate.com/simple-talk/databases/sql-server/learn/check-your-digits/">Check your Digits</a></blockquote><iframe sandbox="allow-scripts" security="restricted" src="https://www.red-gate.com/simple-talk/databases/sql-server/learn/check-your-digits/embed/#?secret=Ynk21Cku8a" width="600" height="338" title="“Check your Digits” — Simple Talk" data-secret="Ynk21Cku8a" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" class="wp-embedded-content"></iframe><script type="text/javascript"> /* <![CDATA[ */ /*! This file is auto-generated */ !function(d,l){"use strict";l.querySelector&&d.addEventListener&&"undefined"!=typeof URL&&(d.wp=d.wp||{},d.wp.receiveEmbedMessage||(d.wp.receiveEmbedMessage=function(e){var t=e.data;if((t||t.secret||t.message||t.value)&&!/[^a-zA-Z0-9]/.test(t.secret)){for(var s,r,n,a=l.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),o=l.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),c=new RegExp("^https?:$","i"),i=0;i<o.length;i++)o[i].style.display="none";for(i=0;i<a.length;i++)s=a[i],e.source===s.contentWindow&&(s.removeAttribute("style"),"height"===t.message?(1e3<(r=parseInt(t.value,10))?r=1e3:~~r<200&&(r=200),s.height=r):"link"===t.message&&(r=new URL(s.getAttribute("src")),n=new URL(t.value),c.test(n.protocol))&&n.host===r.host&&l.activeElement===s&&(d.top.location.href=t.value))}},d.addEventListener("message",d.wp.receiveEmbedMessage,!1),l.addEventListener("DOMContentLoaded",function(){for(var e,t,s=l.querySelectorAll("iframe.wp-embedded-content"),r=0;r<s.length;r++)(t=(e=s[r]).getAttribute("data-secret"))||(t=Math.random().toString(36).substring(2,12),e.src+="#?secret="+t,e.setAttribute("data-secret",t)),e.contentWindow.postMessage({message:"ready",secret:t},"*")},!1)))}(window,document); //# sourceURL=https://www.red-gate.com/simple-talk/wp-includes/js/wp-embed.min.js /* ]]> */ </script> The most persistent struggle in data processing has been to ensure clean data. There are many ways that data can be incorrect and a database must check, as best it can, that the data is correct. The CHECK constraint is ideally suited for this sort of work, and the checking routine can become quite complex when dealing with check digits in data.https://www.red-gate.com/simple-talk/wp-content/uploads/2024/07/simple-talk-dark-background.jpg15001000