Category : MySQL snippets


In attempting to use the mysqldump utility provided with MySQL 8.x against a 5.7 server, you may receive the following error message: mysqldump: Couldn’t execute ‘SELECT COLUMN_NAME, JSON_EXTRACT(HISTOGRAM, ‘$.”number-of-buckets-specified”‘) This is due to the INFORMATION_SCHEMA in 8.0 having more columns to support several new features in 8.x.  This error can be silenced by adding the ..

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— SQL snippet to calculate table fragmentation. SELECT table_schema, TABLE_NAME, ROUND(DATA_LENGTH / 1024 / 1024) AS data_length, ROUND(INDEX_LENGTH / 1024 / 1024) AS index_length, ROUND(DATA_FREE / 1024 / 1024) AS data_free, CONCAT( ROUND( ( data_free / (index_length + data_length) ) * 100 ), ‘%’ ) AS frag_ratio FROM information_schema.tables WHERE DATA_FREE > 0 AND TABLE_SCHEMA ..

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Suppose I try to create a table with a primary key that’s varchar(500), and MySQL complains the key length is longer than the maximum of 1000 bytes. 500 is less than 1000. What’s happening? Plus, a tasty (yet apparently harmless) bug in MySQL. Here’s a statement that will fail on most servers: CREATE TABLE test(c ..

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To rename a schema (emulating the now-dropped RENAME DATABASE functionality): SELECT concat(‘RENAME TABLE oldSchema.’,table_name, ‘ TO newSchema.’,table_name, ‘;’) FROM information_schema.TABLES WHERE table_schema=’oldSchema’; Execute the resultant sql, then drop the now-empty old sche..

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MySQL is SO irritating in its timestamp limitations, in that you can only have one default timestamp column. (Update 6/12/2013: in version 5.6.x, this restriction will be lifted, so I hear) However, you *can* trick MySQL like this. You can use only one of the definitions in one table. Create both timestamp columns like so: ..

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Various ways to get sizing, counts, etc. — Total rows and size for an entire server, excluding system schemata, ordered by size DESC SELECT table_schema,table_name, CONCAT(ROUND(SUM(table_rows) / 1000000,2),’M’) rows, CONCAT(ROUND(SUM(data_length) / (1024 * 1024 * 1024),2), ‘G’) DATA, CONCAT(ROUND(SUM(index_length) / (1024 * 1024 * 1024), 2),’G’) idx, CONCAT(ROUND(SUM(data_length + index_length) / (1024 * 1024 * ..

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It sucks, but sometimes ya gotta. You can’t DROP multiple tables, a parent table or a child table until you disable foreign key checks four your current database. Or for that matter, TRUNC the table, either. To disable/enable foreign key checks, use the following syntax. (Don’t ever disable @@GLOBAL, unless you’re really irritated and have ..

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mysqldump will backup by default all the triggers but NOT the stored procedures/functions. There are 2 mysqldump parameters that control this behavior: * –routines – FALSE by default * –triggers – TRUE by default This means that if you want to include in an existing backup script also the triggers and stored procedures you only ..

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Various crap. SELECT d.id, d.name FROM ireit_analysis.v_ireit_house d, ireit_reference.dictionary_newage r WHERE d.name REGEXP r.word AND ( r.word LIKE ‘%finance%’ || r.definition LIKE ‘%finance%’ || r.word LIKE ‘%bank%’ || r.definition LIKE ‘%bank%’ || r.word LIKE ‘%money%’ || r.definition LIKE ‘%money%’); SELECT d.id, d.name FROM ireit_analysis.v_ireit_house d WHERE d.name STRCMP(SELECT r.word FROM ireit_reference.dictionary_newage r WHERE r.word LIKE ..

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Useful when migrating. Point at source DB instance, retrieve grants using this script, pipe through the Add a semicolon in PERL script, and voila, recreate grants on destination instance. #!/bin/bash ( mysql –batch –skip-column-names -e “SELECT user, host FROM user” mysql ) | while read user host do echo “# $user @ $host” mysql –batch ..

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CONVERT ALL THE THINGS. Well, almost all the things. #!/bin/bash for database in aaaaa bbbbb ccccc ddddd eeee do thesetables=`mysql -N -B -e “SELECT CONCAT(TABLE_SCHEMA,’.’,TABLE_NAME) \ FROM information_schema.TABLES where TABLE_SCHEMA = \”$database\”” \ AND TABLE_SCHEMA NOT IN (‘mysql’,’information_schema’,’performance_schema’)` alltables=`echo $alltables $thesetables` # change the schema itself mysql -e “ALTER DATABASE $database CHARACTER SET utf8 COLLATE ..

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SELECT d.id, d.name, CONCAT_WS(‘ -> ‘,c5.name,c4.name,c3.name,c2.name,c1.name) as cat_string FROM domain d LEFT JOIN category c1 ON c1.id = d.category_id LEFT JOIN category c2 ON c1.parent_id = c2.id LEFT JOIN category c3 ON c2.parent_id = c3.id LEFT JOIN category c4 ON c3.parent_id = c4.id LEFT JOIN category c5 ON c4.parent_i..

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