sqlite update 用法

最新推荐文章于 2025-03-07 06:05:14 发布

nanyuanhao0811

最新推荐文章于 2025-03-07 06:05:14 发布

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本文链接：https://blog.youkuaiyun.com/nanyuanhao0811/article/details/25387519

本文介绍了一种通过SQL更新数据库中图层缩放级别的方法。该方法利用了EXISTS子句来设置外部查询条件，并根据特定的图层特征类排除了一些城市中心点等特定类型。

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UPDATE bmd_layer_tiles \n\
SET ScaleSubLevel = (SELECT bls.ScaleValue \n\
FROM bmd_layer_scalesublevel bls \n\
WHERE " + tblJoin + " \n\
AND ( (bls.ISOConCode = '---') \n\
OR (bls.ISOConCode = bmd_layer_tiles.ISOConCode) )) \n\
WHERE bmd_layer_tiles.featureClass != " +
Ndh2NDS::LexicalCast<std::string>( Layer::finishNDS->m_attrConvert->convert( Ndh2NDSGlobal::POINT_CITY_CENTRE ) ) +
" AND bmd_layer_tiles.featureClass != " +
Ndh2NDS::LexicalCast<std::string>( Layer::finishNDS->m_attrConvert->convert( Ndh2NDSGlobal::POINT_CITY_DISTRICT_CENTRE ) ) +
" AND bmd_layer_tiles.featureClass != " +
Ndh2NDS::LexicalCast<std::string>( Layer::finishNDS->m_attrConvert->convert( Ndh2NDSGlobal::POINT_HAMLET ) ) +" \
AND EXISTS (SELECT 1 \n\
FROM bmd_layer_scalesublevel bls \n\
WHERE " + tblJoin + " \n\
AND ( (bls.ISOConCode = '---') \n\

OR (bls.ISOConCode = bmd_layer_tiles.ISOConCode) ));

通过EXISTS 外部设定查询条件。