Why does this SQL lock table block readers?

Why does this SQL lock table block readers in production. The SQL code runs a long update in a transaction, holding locks and blocking reads. In SQL services this causes latency spikes and timeouts.

#whatswrongwiththissqlquery #sqlbug #sqlproductionbug #sqldebugging #sqldatabase #sqlcodereview #sqlperformance #sqlreliability #sqlanalytics #sqldataintegrity #sqlengineering #sqllock #sqltransaction #sqlla...

https://www.youtube.com/watch?v=s_mcOfxOi3s

Why does this SQL lock table block readers? #sqldebugging

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